RESUMEN
The African buffalo (Syncerus caffer) is a wild bovid with a historical distribution across much of sub-Saharan Africa. Genomic analysis can provide insights into the evolutionary history of the species, and the key selective pressures shaping populations, including assessment of population level differentiation, population fragmentation, and population genetic structure. In this study we generated the highest quality de novo genome assembly (2.65 Gb, scaffold N50 69.17 Mb) of African buffalo to date, and sequenced a further 195 genomes from across the species distribution. Principal component and admixture analyses provided little support for the currently described four subspecies. Estimating Effective Migration Surfaces analysis suggested that geographical barriers have played a significant role in shaping gene flow and the population structure. Estimated effective population sizes indicated a substantial drop occurring in all populations 5-10,000 years ago, coinciding with the increase in human populations. Finally, signatures of selection were enriched for key genes associated with the immune response, suggesting infectious disease exert a substantial selective pressure upon the African buffalo. These findings have important implications for understanding bovid evolution, buffalo conservation and population management.
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Búfalos , Genoma , Genómica , Búfalos/genética , Animales , Genómica/métodos , Flujo Génico , África del Sur del Sahara , Genética de Población , Filogenia , Variación GenéticaRESUMEN
Theileria equi (T. equi) is an apicomplexan parasite that causes severe hemolytic anemia in equids. Presently, there is inadequate knowledge of the immune responses induced by T. equi in equid hosts impeding understanding of the host parasite relationship and development of potent vaccines for control of T. equi infections. The objective of this study was to evaluate the host-parasite dynamics between T. equi merozoites and infected horses by assessing cytokine expression during primary and secondary parasite exposure, and to determine whether the pattern of expression correlated with clinical indicators of disease. Our findings showed that the expression of pro-inflammatory cytokines was very low and inconsistent during both primary and secondary infection. There was also no correlation between the symptoms observed during primary infection and expression of the cytokines. This suggests that the symptoms might have occurred primarily due to hemolysis and likely not the undesirable effects of pro-inflammatory responses. However, IL-10 and TGF-ß1 were highly expressed in both phases of infection, and their expression was linked to antibody production but not moderation of pro-inflammatory cytokine responses.
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Enfermedades de los Caballos , Interleucina-10 , Theileria , Theileriosis , Factor de Crecimiento Transformador beta1 , Animales , Caballos , Theileriosis/inmunología , Theileriosis/parasitología , Interleucina-10/metabolismo , Interleucina-10/inmunología , Theileria/inmunología , Factor de Crecimiento Transformador beta1/metabolismo , Enfermedades de los Caballos/inmunología , Enfermedades de los Caballos/parasitología , Merozoítos/inmunología , Anticuerpos Antiprotozoarios/inmunología , Formación de Anticuerpos/inmunología , Citocinas/metabolismo , Interacciones Huésped-Parásitos/inmunologíaRESUMEN
African swine fever (ASF) is a contagious viral disease that affects domestic pigs and wild boars, causing significant economic losses globally. After the first Nigerian outbreak in 1997, there have been frequent reports of ASF in pig-producing regions in the country. To facilitate control, it is important to understand the genotype and phylogenetic relationship of ASF viruses (ASFVs). Recent genetic analysis of Nigerian ASFV isolates has revealed the presence of both genotypes I and II; this is based on analysis of a few selected genes. Phylogenetic analysis of ASFV whole genomes highlights virus origins and evolution in greater depth. However, there is currently no information on the ASFV genome from Nigerian isolates. Two ASFV-positive samples were detected during a random survey of 150 Nigerian indigenous pig samples collected in 2016. We assembled near-complete genomes of the two ASFV-positive samples using in-solution hybrid capture sequencing. The genome-wide phylogenetic tree assigned these two genomes into p72 genotype I, particularly close to the virulent Benin 97/1 strain. The two ASFVs share 99.94 and 99.92â% genomic sequence identity to Benin97/1. This provides insight into the origin and relationship of ASFV strains from Nigeria and Italy. The study reports for the first time the determination of near-complete genomes of ASFV using in-solution hybrid capture sequencing, which represents an important advance in understanding the global evolutionary landscape of ASFVs.
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Fiebre Porcina Africana , Porcinos , Animales , Filogenia , Genotipo , Genómica , Brotes de Enfermedades , Sus scrofaRESUMEN
A meeting, sponsored by the Bill and Melinda Gates Foundation (BMGF) and organised by Clinglobal, was held at The International Livestock Research Institute (ILRI) in Nairobi, Kenya, from 19th - to 21st October 2022. The meeting assembled a unique group of experts on tick control in Africa. Academia, international agencies (FAO and ILRI), the private Animal Health sector and government veterinary services were represented. The significant outcomes included: (i) a shared commitment to standardisation and improvement of acaricide resistance bioassay protocols, particularly the widely used larval packet test (LPT); (ii) development of novel molecular assays for detecting acaricide resistance; (3) creation of platforms for disseminating acaricide resistance data to farmers, veterinary service providers and veterinary authorities to enable more rational evidence-based control of livestock ticks. Implementation of enhanced control will be facilitated by several recently established networks focused on control of parasites in Africa and globally, whose activities were presented at the meeting. These include a newly launched community of practice on management of livestock ticks, coordinated by FAO, an African module of the World Association for the Advancement of Veterinary Parasitology (WAAVP-AN) and the MAHABA (Managing Animal Health and Acaricides for a Better Africa) initiative of Elanco Animal Health.
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Acaricidas , Enfermedades de los Bovinos , Rhipicephalus , Infestaciones por Garrapatas , Enfermedades por Picaduras de Garrapatas , Animales , Bovinos , Acaricidas/farmacología , Kenia/epidemiología , Enfermedades por Picaduras de Garrapatas/epidemiología , Enfermedades por Picaduras de Garrapatas/prevención & control , Enfermedades por Picaduras de Garrapatas/veterinaria , Enfermedades de los Bovinos/diagnóstico , Enfermedades de los Bovinos/tratamiento farmacológico , Enfermedades de los Bovinos/epidemiología , Infestaciones por Garrapatas/epidemiología , Infestaciones por Garrapatas/prevención & control , Infestaciones por Garrapatas/veterinariaRESUMEN
The range of the protozoan parasite Theileria parva, which causes East Coast fever in cattle, has been expanding to countries where it has not previously been detected, as a result of cross-border domestic cattle movement. Countries where T. parva has not previously been observed until recently include Cameroon and South Sudan. This raises the issue of the conservation of the p104 antigen gene, on which the nested PCR assay that is widely used for T. parva surveillance in the blood of infected cattle is based. We sampled 40 isolates from six countries widely distributed across the geographical range of the parasite, including eastern, central and southern Africa, for p104 sequence polymorphism. These included parasites from both domestic cattle and the Cape buffalo (Syncerus caffer) wildlife reservoir. The most frequent allelic variants were present in cattle transmissible isolates from multiple widely separated geographical regions in Zambia, Uganda, Kenya, Tanzania, Rwanda and South Africa. These frequent p104 variants were also present in the three component stocks of the Muguga cocktail used for the infection and treatment live immunisation procedure to control T. parva in the field. Other isolates exhibited unique alleles. This includes some of the p104 sequences from Cameroon, which is outside the known range of the Rhipicephalus tick vector and whose origin is therefore unclear. The nested primer oligonucleotides used to generate the amplicons were universally conserved in cattle-derived parasites and a majority of buffalo-derived isolates across the geographical range of the parasite. However, some rare South African buffalo-derived isolates exhibited one or two mismatches with the primer sequences. It therefore remains possible that some p104 alleles may be so divergent that they do not amplify with the current diagnostic primers and are not detectable in surveys, hence the need for increasing knowledge of genetic heterogeneity of diagnostic targets. There was no evidence for positive selection among those p104 mutations that resulted in residue changes. Importantly, the data indicate that the p104-based PCR detection assay should be effective across the majority of the range of T. parva, and if the one or two mismatches are shown in future to result in the primers annealing less efficiently, then the assay can be further improved by introduction of degenerate bases to enable amplification of the less frequent South African buffalo-derived variant p104 genes.
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Parásitos , Rhipicephalus , Theileria parva , Theileriosis , Animales , Bovinos , Theileria parva/genética , Parásitos/genética , Búfalos/parasitología , Theileriosis/epidemiología , Theileriosis/parasitología , Rhipicephalus/parasitología , Reacción en Cadena de la Polimerasa/veterinaria , Variación GenéticaRESUMEN
African wild suids consist of several endemic species that represent ancient members of the family Suidae and have colonized diverse habitats on the African continent. However, limited genomic resources for African wild suids hinder our understanding of their evolution and genetic diversity. In this study, we assembled high-quality genomes of a common warthog (Phacochoerus africanus), a red river hog (Potamochoerus porcus), as well as an East Asian Diannan small-ear pig (Sus scrofa). Phylogenetic analysis showed that common warthog and red river hog diverged from their common ancestor around the Miocene/Pliocene boundary, putatively predating their entry into Africa. We detected species-specific selective signals associated with sensory perception and interferon signaling pathways in common warthog and red river hog, respectively, which contributed to their local adaptation to savannah and tropical rainforest environments, respectively. The structural variation and evolving signals in genes involved in T-cell immunity, viral infection, and lymphoid development were identified in their ancestral lineage. Our results provide new insights into the evolutionary histories and divergent genetic adaptations of African suids.
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Adaptación Fisiológica , Animales , Porcinos , Filogenia , Especificidad de la Especie , Adaptación Fisiológica/genética , ÁfricaRESUMEN
We describe the characterization of an African swine fever genotype IX virus (ASFV-Kenya-IX-1033), which was isolated from a domestic pig in western Kenya during a reported outbreak. This includes the efficiency of virus replication and in vivo virulence, together with genome stability and virulence, following passage in blood macrophages and in a wild boar lung cell line (WSL). The ASFV-Kenya-IX-1033 stock retained its ability to replicate in primary macrophages and retained virulence in vivo, following more than 20 passages in a WSL. At the whole genome level, a few single-nucleotide differences were observed between the macrophage and WSL-propagated viruses. Thus, we propose that the WSL is suitable for the production of live-attenuated ASFV vaccine candidates based on the modification of this wild-type isolate. The genome sequences for ASFV-Kenya-IX-1033 propagated in macrophages and in WSL cells were submitted to GenBank, and a challenge model based on the isolate was developed. This will aid the development of vaccines against the genotype IX ASFV circulating in eastern and central Africa.
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Virus de la Fiebre Porcina Africana , Fiebre Porcina Africana , Animales , Línea Celular , Kenia , Nucleótidos , Sus scrofa , Porcinos , Vacunas AtenuadasRESUMEN
Infection of pigs with the African swine fever virus (ASFV) leads to a devastating hemorrhagic disease with a high mortality of up to 100%. In this study, a CD2v gene deletion was introduced to a genotype IX virus from East Africa, ASFV-Kenya-IX-1033 (ASFV-Kenya-IX-1033-∆CD2v), to investigate whether this deletion led to reduced virulence in domestic pigs and to see if inoculation with this LA-ASFV could induce protective immunity against parental virus challenge. All pigs inoculated with ASFV-Kenya-IX-1033-ΔCD2v survived inoculation but presented with fever, reduced appetite and lethargy. ASFV genomic copies were detected in only one animal at one time point. Seven out of eight animals survived subsequent challenge with the pathogenic parental strain (87.5%) but had mild to moderate clinical symptoms and had a gross pathology compatible with chronic ASFV infection. All mock-immunised animals developed acute ASF upon challenge with ASFV-Kenya-IX-1033 and were euthanised upon meeting the humane endpoint criteria. ASFV genome copy numbers after challenge were similar in the two groups. ASFV-Kenya-IX-1033-∆CD2v is therefore a useful tool to investigate the development of immunity to ASFV genotype IX, but safety concerns preclude its use as a candidate vaccine without further attenuation.
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Virus de la Fiebre Porcina Africana , Fiebre Porcina Africana , Vacunas Virales , Fiebre Porcina Africana/prevención & control , Animales , Eliminación de Gen , Kenia , Sus scrofa , Porcinos , Vacunas Virales/genética , Virulencia/genéticaRESUMEN
African Swine Fever Virus (ASFV) poses a serious threat to the pork industry worldwide; however, there is no safe vaccine or treatment available. The development of an efficacious subunit vaccine will require the identification of protective antigens. The ASFV pp220 polyprotein is essential for virus structural integrity. This polyprotein is processed to generate p5, p34, p14, p37, and p150 individual proteins. Immunization of pigs with a cocktail of adenoviruses expressing the proteins induced significant IgG, IFN-γ-secreting cells, and cytotoxic T lymphocyte responses. Four predicted SLA-I binding nonamer peptides, namely p34161-169, p37859-867, p1501363-1371, and p1501463-1471, recalled strong IFN-γ+ PBMC and splenocyte responses. Notably, peptide p34161-169 was recognized by PBMCs isolated from 7/10 pigs and by splenocytes isolated from 8/10 pigs. Peptides p37859-867 and p1501363-1371 stimulated recall IFN-γ+ responses in PBMCs and splenocytes isolated from 8/10 pigs, whereas peptide p1501463-1471 recalled responses in PBMCs and splenocytes isolated from 7/10 to 9/10 pigs, respectively. The results demonstrate that the pp220 polyprotein contains multiple epitopes that induce robust immune responses in pigs. Importantly, these epitopes are 100% conserved among different ASFV genotypes and were predicted to bind multiple SLA-I alleles. The outcomes suggest that pp220 is a promising candidate for inclusion in a prototype subunit vaccine.
RESUMEN
In many African countries, tick control has recently been the responsibility of resource-poor farmers rather than central government veterinary departments. This has led to an increase in acaricide resistance, threatening the welfare of livestock farmers in sub-Saharan Africa. Resistance has evolved to the three classes of acaricides used most extensively in the continent, namely fourth-generation synthetic pyrethroids (SP), organophosphates (OP) and amidines (AM), in virtually all countries in which they have been deployed across the globe. Most current data are derived from research in Australia and Latin America, with the majority of studies on acaricide resistance in Africa performed in South Africa. There is also limited recent research from West Africa and Uganda. These studies confirm that acaricide resistance in cattle ticks is a major problem in Africa. Resistance is most frequently directly assayed in ticks using the larval packet test (LPT) that is endorsed by FAO, but such tests require a specialist tick-rearing laboratory and are relatively time consuming. To date they have only been used on a limited scale in Africa and resistance is often still inferred from tick numbers on animals. Rapid tests for resistance in ticks, would be better than the LPT and are theoretically possible to develop. However, these are not yet available. Resistance can be mitigated through integrated control strategies, comprising a combination of methods, including acaricide class rotation or co-formulations, ethnoveterinary practices, vaccination against ticks and modified land management use by cattle, with the goal of minimising the number of acaricide applications required per year. There are data suggesting that small-scale farmers in Africa are often unaware of the chemical differences between different acaricide brands and use these products at concentrations other than those recommended by the manufacturers, or in incorrect rotations or combinations of the different classes of chemicals on the market. There is an urgent need for a more evidence-based approach to acaricide usage in small-scale livestock systems in Africa, including direct measurements of resistance levels, combined with better education of farmers regarding acaricide products and how they should be deployed for control of livestock ticks.
RESUMEN
BACKGROUND: Among protozoan parasites in the genus Babesia, Babesia bigemina is endemic and widespread in the East African region while the status of the more pathogenic Babesia bovis remains unclear despite the presence of the tick vector, Rhipicephalus microplus, which transmits both species. Recent studies have confirmed the occurrence of R. microplus in coastal Kenya, and although B. bovis DNA has previously been detected in cattle blood in Kenya, no surveillance has been done to establish its prevalence. This study therefore investigated the occurrence of B. bovis in cattle in Kwale County, Kenya, where R. microplus is present in large numbers. METHODS: A species-specific multiplex TaqMan real-time PCR assay targeting two Babesia bovis genes, 18S ribosomal RNA and mitochondrially-encoded cytochrome b and B. bigemina cytochrome b gene was used to screen 506 cattle blood DNA samples collected from Kwale County for presence of Babesia parasite DNA. A sub-set of 29 B. bovis real-time PCR-positive samples were further amplified using a B. bovis-specific spherical body protein-4 (SBP-4) nested PCR and the resulting products sequenced to confirm the presence of B. bovis. RESULTS: A total of 131 animals (25.8%) were found to have bovine babesiosis based on real-time PCR. Twenty-four SBP4 nucleotide sequences obtained matched to B. bovis with a similarity of 97-100%. Of 131 infected animals, 87 (17.2%) were positive for B. bovis while 70 (13.8%) had B. bigemina and 26 (5.1%) were observed to be co-infected with both Babesia species. A total of 61 animals (12.1%) were found to be infected with B. bovis parasites only, while 44 animals (8.7%) had B. bigemina only. Babesia bovis and B. bigemina infections were detected in the three Kwale sub-counties. CONCLUSION: These findings reveal high prevalence of pathogenic B. bovis in a Kenyan area cutting across a busy transboundary livestock trade route with neighbouring Tanzania. The Babesia multiplex real-time PCR assay used in this study is specific and can detect and differentiate the two Babesia species and should be used for routine B. bovis surveillance to monitor the spread and establishment of the pathogen in other African countries where B. bigemina is endemic. Moreover, these findings highlight the threat of fatal babesiosis caused by B. bovis, whose endemic status is yet to be established. GRAPHICAL ABTRACT.
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Babesia bovis , Babesia , Babesiosis , Enfermedades de los Bovinos , Parásitos , Rhipicephalus , Animales , Babesia/genética , Babesia bovis/genética , Babesiosis/epidemiología , Babesiosis/parasitología , Bovinos , Enfermedades de los Bovinos/epidemiología , Enfermedades de los Bovinos/parasitología , Citocromos b/genética , ADN Protozoario/genética , Kenia/epidemiología , Parásitos/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Rhipicephalus/genéticaRESUMEN
Theileria equi is an obligate intracellular protozoan parasite that causes severe hemolytic anaemia in most equid species. Similar to other apicomplexan parasites, T. equi contains rhoptries whose contents have been implicated in host cell invasion and formation of the parasitophorous vacuole that is crucial for survival of the species within cells. Despite their importance, the composition of T. equi rhoptries and their role(s) in host cell invasion remain unexplored. To gain insight into these issues, we evaluated the expression, immunogenicity, and functional roles of two T. equi rhoptry-associated proteins abbreviated as RAP-1a and RAP-1b. The full-length RAP-1a protein was expressed to perform the analysis but our efforts to express the full-length RAP-1b protein failed due to an unknown reason. We therefore generated synthetic immunogenic peptides that map onto the N- and C-termini of the RAP-1b protein as an alternative approach. Our findings show that both proteins are expressed in the extracellular and intra-erythrocytic merozoite stages of T. equi. Serological analyses show that T. equi-infected horses mount antibody responses that recognise both proteins and correlate with a decrease in T. equi load in both acutely and persistently infected horses. In vitro neutralisation studies show that the T. equi RAP-1a protein contains neutralisation-sensitive epitopes as antibodies developed against the protein significantly inhibited the parasites from invading equine erythrocytes. Conversely, antibodies developed against the RAP-1b synthetic peptides did not neutralise parasite invasion, showing that the protein regions on which the peptides were based are not required for T. equi invasion. Overall, the data shows that T. equi rhoptries and their contents are involved in invasion of host cells and supports T. equi RAP-1 proteins as candidates for developing novel serodiagnosis tools and vaccines.
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Enfermedades de los Caballos , Theileria , Theileriosis , Vacunas , Animales , Bovinos , Epítopos , Enfermedades de los Caballos/diagnóstico , Enfermedades de los Caballos/prevención & control , Caballos , Merozoítos , Theileriosis/prevención & controlRESUMEN
African swine fever (ASF) caused by the African swine fever virus (ASFV) is ranked by OIE as the most important source of mortality in domestic pigs globally and is indigenous to African wild suids and soft ticks. Despite two ASFV genotypes causing economically devastating epidemics outside the continent since 1961, there have been no genome-level analyses of virus evolution in Africa. The virus was recently transported from south-eastern Africa to Georgia in 2007 and has subsequently spread to Russia, eastern Europe, China, and south-east Asia with devastating socioeconomic consequences. To date, two of the 24 currently described ASFV genotypes defined by sequencing of the p72 gene, namely genotype I and II, have been reported outside Africa, with genotype II being responsible for the ongoing pig pandemic. Multiple complete genotype II genome sequences have been reported from European, Russian and Chinese virus isolates but no complete genome sequences have yet been reported from Africa. We report herein the complete genome of a Tanzanian genotype II isolate, Tanzania/Rukwa/2017/1, collected in 2017 and determined using an Illumina short read strategy. The Tanzania/Rukwa/2017/1 sequence is 183,186 bp in length (in a single contig) and contains 188 open reading frames. Considering only un-gapped sites in the pairwise alignments, the new sequence has 99.961% identity with the updated Georgia 2007/1 reference isolate (FR682468.2), 99.960% identity with Polish isolate Pol16_29413_o23 (MG939586) and 99.957% identity with Chinese isolate ASFV-wbBS01 (MK645909.1). This represents 73 single nucleotide polymorphisms (SNPs) relative to the Polish isolate and 78 SNPs with the Chinese genome. Phylogenetic analysis indicated that Tanzania/Rukwa/2017/1 clusters most closely with Georgia 2007/1. The majority of the differences between Tanzania/Rukwa/2017/1 and Georgia 2007/1 genotype II genomes are insertions/deletions (indels) as is typical for ASFV. The indels included differences in the length and copy number of the terminal multicopy gene families, MGF 360 and 110. The Rukwa2017/1 sequence is the first complete genotype II genome from a precisely mapped locality in Africa, since the exact origin of Georgia2007/1 is unknown. It therefore provides baseline information for future analyses of the diversity and phylogeography of this globally important genetic sub-group of ASF viruses.
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Virus de la Fiebre Porcina Africana/genética , Fiebre Porcina Africana/epidemiología , Fiebre Porcina Africana/genética , África/epidemiología , Fiebre Porcina Africana/virología , Animales , ADN Viral/genética , Brotes de Enfermedades/veterinaria , Europa (Continente)/epidemiología , Genoma Viral/genética , Genotipo , Secuenciación de Nucleótidos de Alto Rendimiento/métodos , Pandemias/veterinaria , Filogenia , Análisis de Secuencia de ADN/métodos , Sus scrofa/genética , Porcinos , Secuenciación Completa del Genoma/métodosRESUMEN
Theileria equi is a widely distributed apicomplexan parasite that causes severe hemolytic anemia in equid species. There is currently no effective vaccine for control of the parasite and understanding the mechanism that T. equi utilizes to invade host cells may be crucial for vaccine development. Unlike most apicomplexan species studied to date, the role of micronemes in T. equi invasion of host cells is unknown. We therefore assessed the role of the T. equi claudin-like apicomplexan microneme protein (CLAMP) in the invasion of equine erythrocytes as a first step towards understanding the role of this organelle in the parasite. Our findings show that CLAMP is expressed in the merozoite and intra-erythrocytic developmental stages of T. equi and in vitro neutralization experiments suggest that the protein is involved in erythrocyte invasion. Proteomic analyses indicate that CLAMP interacts with the equine erythrocyte α-and ß- spectrin chains in the initial stages of T. equi invasion and maintains these interactions while also associating with the anion-exchange protein, tropomyosin 3, band 4.1 and cytoplasmic actin 1 after invasion. Additionally, serological analyses show that T. equi-infected horses mount robust antibody responses against CLAMP indicating that the protein is immunogenic and therefore represents a potential vaccine candidate.
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Membrana Eritrocítica/metabolismo , Enfermedades de los Caballos/parasitología , Proteínas Protozoarias/inmunología , Proteínas Protozoarias/metabolismo , Theileria/patogenicidad , Theileriosis/parasitología , Animales , Anticuerpos Antiprotozoarios/sangre , Anticuerpos Antiprotozoarios/inmunología , Antígenos de Protozoos/inmunología , Proteínas Sanguíneas/metabolismo , Claudinas , Epítopos de Linfocito B/inmunología , Eritrocitos/parasitología , Enfermedades de los Caballos/inmunología , Caballos/sangre , Caballos/parasitología , Proteínas de la Membrana/química , Proteínas de la Membrana/genética , Proteínas de la Membrana/inmunología , Proteínas de la Membrana/metabolismo , Merozoítos/genética , Merozoítos/metabolismo , Pruebas de Neutralización , Proteínas Protozoarias/química , Proteínas Protozoarias/genética , Theileria/crecimiento & desarrollo , Theileria/inmunología , Theileria/metabolismo , Theileriosis/inmunologíaRESUMEN
BACKGROUND: Tick-borne diseases (TBDs) constitute a major constraint for livestock development in sub-Saharan Africa, with East Coast fever (ECF) being the most devastating TBD of cattle. However, in Burundi, detailed information is lacking on the current prevalence of TBDs and on the associated economic losses from mortality and morbidity in cattle as well as the costs associated with TBD control and treatment. The aim of this study was, therefore, to assess the prevalence and spatial distribution of tick-borne pathogens (TBPs) in cattle across the major agro-ecological zones (AEZs) in Burundi. METHODS: In a cross-sectional study conducted in ten communes spanning the five main AEZs in Burundi, blood samples were taken from 828 cattle from 305 farms between October and December 2017. Evidence of Theileria parva infection was assessed by antibody level, measured using a polymorphic immunodominant molecule (PIM) antigen-based enzyme-linked immunosorbent assay (ELISA) and by a T. parva-specific p104 gene-based nested PCR. Antibodies against Theileria mutans infection were detected using the 32-kDa antigen-based indirect ELISA, while the 200-kDa antigen and the major surface protein 5 (MSP5)-based indirect ELISA were used to detect antibodies against Babesia bigemina and Anaplasma marginale, respectively. RESULTS: The prevalence of T. parva across the ten communes sampled ranged from 77.5 to 93.1% and from 67.8 to 90.0% based on the ELISA and PCR analysis, respectively. A statistically significant difference in infection was observed between calves and adult cattle; however, T. parva infection levels were not significantly associated with sex and breed. The seroprevalence indicating exposure to T. mutans, B. bigemina and A. marginale ranged from 30 to 92.1%, 33.7 to 90% and 50 to 96.2%, respectively. Mixed infections of TBPs were detected in 82.91% of cattle sampled, with 11 different combinations of pathogen species detected . CONCLUSIONS: The findings indicate that T. parva, A. marginale and B. bigemina infections are endemic in Burundi. Knowledge of the spatial distribution of TBPs will facilitate the design of effective targeted strategies to control these diseases. There is a need for further investigations of the distribution of tick vectors and the population structure of TBPs in order to identify the key epidemiological factors contributing to TBD outbreaks in Burundi.
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Anaplasmosis/epidemiología , Babesiosis/epidemiología , Enfermedades de los Bovinos/epidemiología , Theileriosis/epidemiología , Enfermedades por Picaduras de Garrapatas/epidemiología , Garrapatas/parasitología , Anaplasma marginale/inmunología , Anaplasmosis/transmisión , Distribución Animal , Animales , Anticuerpos Antiprotozoarios/sangre , Babesia/inmunología , Babesiosis/transmisión , Burundi/epidemiología , Bovinos , Enfermedades de los Bovinos/parasitología , Enfermedades de los Bovinos/transmisión , Estudios Transversales , Enfermedades Endémicas , Femenino , Masculino , Prevalencia , Estudios Seroepidemiológicos , Theileria parva/inmunología , Theileriosis/inmunología , Theileriosis/transmisión , Enfermedades por Picaduras de Garrapatas/transmisiónRESUMEN
Theileria parva is an economically important, intracellular, tick-transmitted parasite of cattle. A live vaccine against the parasite is effective against challenge from cattle-transmissible T. parva but not against genotypes originating from the African Cape buffalo, a major wildlife reservoir, prompting the need to characterize genome-wide variation within and between cattle- and buffalo-associated T. parva populations. Here, we describe a capture-based target enrichment approach that enables, for the first time, de novo assembly of nearly complete T. parva genomes derived from infected host cell lines. This approach has exceptionally high specificity and sensitivity and is successful for both cattle- and buffalo-derived T. parva parasites. De novo genome assemblies generated for cattle genotypes differ from the reference by ~54K single nucleotide polymorphisms (SNPs) throughout the 8.31 Mb genome, an average of 6.5 SNPs/kb. We report the first buffalo-derived T. parva genome, which is ~20 kb larger than the genome from the reference, cattle-derived, Muguga strain, and contains 25 new potential genes. The average non-synonymous nucleotide diversity (πN) per gene, between buffalo-derived T. parva and the Muguga strain, was 1.3%. This remarkably high level of genetic divergence is supported by an average Wright's fixation index (FST), genome-wide, of 0.44, reflecting a degree of genetic differentiation between cattle- and buffalo-derived T. parva parasites more commonly seen between, rather than within, species. These findings present clear implications for vaccine development, further demonstrated by the ability to assemble nearly all known antigens in the buffalo-derived strain, which will be critical in design of next generation vaccines. The DNA capture approach used provides a clear advantage in specificity over alternative T. parva DNA enrichment methods used previously, such as those that utilize schizont purification, is less labor intensive, and enables in-depth comparative genomics in this apicomplexan parasite.
Asunto(s)
Búfalos/parasitología , ADN Protozoario/genética , Variación Genética , Theileria parva/genética , Theileriosis/parasitología , Animales , Bovinos , Genoma de Protozoos , Genotipo , Especificidad de la Especie , Theileria parva/clasificación , Theileria parva/aislamiento & purificaciónRESUMEN
Buffalo-derived Theileria parva can 'break through' the immunity induced by the infection and treatment vaccination method (ITM) in cattle. However, no such 'breakthroughs' have been reported in northern Tanzania where there has been long and widespread ITM use in pastoralist cattle, and the Cape buffalo (Syncerus caffer) is also present. We studied the exposure of vaccinated and unvaccinated cattle in northern Tanzania to buffalo-derived T. parva using p67 gene polymorphisms and compared this to its distribution in vaccinated cattle exposed to buffalo-derived T. parva in central Kenya, where vaccine 'breakthroughs' have been reported. Additionally, we analysed the CD8+ T cell target antigen Tp2 for positive selection. Our results showed that 10% of the p67 sequences from Tanzanian cattle (n = 39) had a buffalo type p67 (allele 4), an allele that is rare among East African isolates studied so far. The percentage of buffalo-derived p67 alleles observed in Kenyan cattle comprised 19% of the parasites (n = 36), with two different p67 alleles (2 and 3) of presumptive buffalo origin. The Tp2 protein was generally conserved with only three Tp2 variants from Tanzania (n = 33) and five from Kenya (n = 40). Two Tanzanian Tp2 variants and two Kenyan Tp2 variants were identical to variants present in the trivalent Muguga vaccine. Tp2 evolutionary analysis did not show evidence for positive selection within previously mapped epitope coding sites. The p67 data indicates that some ITM-vaccinated cattle are protected against disease induced by a buffalo-derived T. parva challenge in northern Tanzania and suggests that the parasite genotype may represent one factor explaining this.
Asunto(s)
Antígenos de Superficie/genética , Búfalos/parasitología , Theileria parva/genética , Theileriosis/parasitología , Alelos , Animales , Animales Salvajes/parasitología , Bovinos , Genotipo , Especificidad del Huésped , Kenia , Ganado/parasitología , Polimorfismo Genético/genética , Esporozoítos/genética , Tanzanía , Theileria parva/clasificación , Theileriosis/transmisión , Vacunación/veterinariaRESUMEN
BACKGROUND: The tick vector Rhipicephalus microplus which transmits Babesia spp. and rickettsial pathogens has not been reported in Kenya since 1998. More recently, the pathogenic Babesia bovis has been detected in cattle blood DNA. The status of R. microplus in Kenya remains unknown. This study employed morphological and molecular tools to characterize R. microplus originating from Kenya and assess the genetic relationships between Kenyan and other African R. microplus genotypes. METHODS: Ticks were collected in south-eastern Kenya (Kwale County) from cattle and characterized to investigate the existence of R. microplus. Genetic and phylogenetic relationships between the Kenyan and other annotated R. microplus reference sequences was investigated by analysis of the cytochrome c oxidase subunit 1 (cox1) gene. To further characterize Kenyan ticks, we generated low coverage whole genome sequences of two R. microplus, one R. decoloratus and R. appendiculatus. A B. bovis specific TaqMan probe qPCR assay was used to detect B. bovis in gDNA from R. microplus ticks. RESULTS: Occurrence of R. microplus was confirmed in Kwale County, Kenya. The Kenyan R. microplus cox1 sequences showed very high pairwise identities (> 99%) and clustered very closely with reference African R. microplus sequences. We found a low genetic variation and lack of geographical sub-structuring among the African cox1 sequences of R. microplus. Four complete mitochondrial (mt) genomes for two R. microplus, one R. decoloratus and one R. appendiculatus were assembled from next generation sequence data. The mitochondrial genome sequences of the two Kenyan R. microplus ticks clustered closely with reference genome sequences from Brazil, USA, Cambodia and India forming R. microplus Clade A. No B. bovis was detected in the Kwale R. microplus DNA. CONCLUSIONS: These findings confirm the presence of R. microplus in Kenya and suggest that R. microplus Clade A is prevalent in cattle in sub-Saharan Africa. These and other recent findings of widespread occurrence of R. microplus in Africa provide a strong justification for urgent surveillance to determine and monitor the spread of R. microplus and vector competence of Boophilus ticks for B. bovis in Africa, with the ultimate goal of strategic control.
Asunto(s)
Babesia bovis/aislamiento & purificación , Rhipicephalus , Infestaciones por Garrapatas/veterinaria , Animales , Vectores Arácnidos/genética , Vectores Arácnidos/parasitología , Babesia bovis/genética , Bovinos , Enfermedades de los Bovinos/epidemiología , Vectores de Enfermedades , Complejo IV de Transporte de Electrones/genética , Monitoreo Epidemiológico , Genes Protozoarios , Genoma Mitocondrial , Kenia/epidemiología , Patología Molecular/métodos , Filogenia , Rhipicephalus/genética , Rhipicephalus/parasitologíaRESUMEN
Equine theileriosis, a tick-transmitted disease caused by the hemoprotozoan parasites Theileria equi and Theileria haneyi, affects equids throughout tropical and subtropical regions of the world. It is a significant regulatory concern in non-endemic countries, where testing for equine theileriosis is required prior to horse import to prevent parasite entry. Within endemic areas, infection causes significant morbidity and mortality, leading to economic losses. No vaccine for equine theileriosis is available, and current drug treatment protocols are inconsistent and associated with significant side effects. Recent work has revealed substantial genetic variability among equine theileriosis organisms, and analysis of ribosomal DNA from affected animals around the world indicates that the organisms can be grouped into five distinct clades. As these diverse parasites are capable of infecting a wide range of both tick and mammalian hosts, movement of different equine Theileria species between endemic countries, and eventually into non-endemic countries, is a significant concern. Furthermore, the substantial genetic variability of these organisms will likely render currently utilized importation diagnostic tests unable to detect all equine Theileria spp. To this end, more complete characterization of these diverse parasites is critical to the continued global control of equine theileriosis. This review discusses current knowledge of equine Theileria spp. in this context, and highlights new opportunities and challenges for workers in this field.
Asunto(s)
Enfermedades de los Caballos/parasitología , Especificidad del Huésped , Mamíferos/parasitología , ARN Ribosómico 18S/genética , Theileria/clasificación , Animales , Variación Genética , Caballos , Filogenia , Theileriosis/parasitologíaRESUMEN
BACKGROUND: The apicomplexan parasite Theileria parva causes a livestock disease called East coast fever (ECF), with millions of animals at risk in sub-Saharan East and Southern Africa, the geographic distribution of T. parva. Over a million bovines die each year of ECF, with a tremendous economic burden to pastoralists in endemic countries. Comprehensive, accurate parasite genome annotation can facilitate the discovery of novel chemotherapeutic targets for disease treatment, as well as elucidate the biology of the parasite. However, genome annotation remains a significant challenge because of limitations in the quality and quantity of the data being used to inform the location and function of protein-coding genes and, when RNA data are used, the underlying biological complexity of the processes involved in gene expression. Here, we apply our recently published RNAseq dataset derived from the schizont life-cycle stage of T. parva to update structural and functional gene annotations across the entire nuclear genome. RESULTS: The re-annotation effort lead to evidence-supported updates in over half of all protein-coding sequence (CDS) predictions, including exon changes, gene merges and gene splitting, an increase in average CDS length of approximately 50 base pairs, and the identification of 128 new genes. Among the new genes identified were those involved in N-glycosylation, a process previously thought not to exist in this organism and a potentially new chemotherapeutic target pathway for treating ECF. Alternatively-spliced genes were identified, and antisense and multi-gene family transcription were extensively characterized. CONCLUSIONS: The process of re-annotation led to novel insights into the organization and expression profiles of protein-coding sequences in this parasite, and uncovered a minimal N-glycosylation pathway that changes our current understanding of the evolution of this post-translational modification in apicomplexan parasites.