Sibling species of the major malaria vector Anopheles gambiae display divergent preferences for aquatic breeding sites in southern Nigeria.

BACKGROUND: When integrated with insecticide-treated bed nets, larval control of Anopheles mosquitoes could fast-track reductions in the incidence of human malaria. However, larval control interventions may deliver suboptimal outcomes where the preferred breeding places of mosquito vectors are not well known. This study investigated the breeding habitat choices of Anopheles mosquitoes in southern Nigeria. The objective was to identify priority sites for mosquito larval management in selected urban and periurban locations where malaria remains a public health burden.  METHODS: Mosquito larvae were collected in urban and periurban water bodies during the wet-dry season interface in Edo, Delta, and Anambra States. Field-collected larvae were identified based on PCR gel-electrophoresis and amplicon sequencing, while the associations between Anopheles larvae and the properties and locations of water bodies were assessed using a range of statistical methods. RESULTS: Mosquito breeding sites were either man-made (72.09%) or natural (27.91%) and mostly drainages (48.84%) and puddles (25.58%). Anopheles larvae occurred in drainages, puddles, stream margins, and a concrete well, and were absent in drums, buckets, car tires, and a water-holding iron pan, all of which contained culicine larvae. Wild-caught Anopheles larvae comprised Anopheles coluzzii (80.51%), Anopheles gambiae sensu stricto (s.s.) (11.54%), and Anopheles arabiensis (7.95%); a species-specific PCR confirmed the absence of the invasive urban malaria vector Anopheles stephensi among field-collected larvae. Anopheles arabiensis, An. coluzzii, and An. gambiae s.s. displayed preferences for turbid, lowland, and partially sunlit water bodies, respectively. Furthermore, An. arabiensis preferred breeding sites located outside 500 m of households, whereas An. gambiae s.s. and An. coluzzii had increased detection odds in sites within 500 m of households. Anopheles gambiae s.s. and An. coluzzii were also more likely to be present in natural water bodies; meanwhile, 96.77% of An. arabiensis were in man-made water bodies. Intraspecific genetic variations were little in the dominant vector An. coluzzii, while breeding habitat choices of populations made no statistically significant contributions to these variations. CONCLUSION: Sibling malaria vectors in the An. gambiae complex display divergent preferences for aquatic breeding habitats in southern Nigeria. The findings are relevant for planning targeted larval control of An. coluzzii whose increasing evolutionary adaptations to urban ecologies are driving the proliferation of the mosquito, and An. arabiensis whose adults typically evade the effects of treated bed nets due to exophilic tendencies.

Endoparasites of Small Mammals in Edo State, Nigeria: Public Health Implications.

Some small mammals occur as household pests and harbour a number of parasites that could be of public health importance. This study profiled the helminth and protozoan parasites in trapped small mammals within and around human dwelling places (houses) located across 4 major towns (Auchi, Benin, Ekpoma, and Uromi) and environs in Edo state, Nigeria. Six genera (Apodemus sp., Crocidura sp., Mastomys natalensis, Mus musculus, Rattus sp., and Sorex sp.) were identified from 502 trapped small mammals. Overall, M. musculus (71.9%) and Rattus rattus (20.1%) were the most frequently trapped. In total, on examination of blood, gastrointestinal contents, and brain tissues, 12 helminth taxa (Angiostrongylus sp., Aspicularis sp., Capillaria sp., Gongylonema sp., Heterakis spumosa, Hymenolepis diminuta, Hymenolepis nana, Mastophorus muris, Moniliformis moniliformis, Nippostrongylus brasiliensis, Strongyloides sp., Trichosomoides sp., and Trichuris sp.), and 6 protozoan parasites (Babesia sp., Trypanosoma lewisi, Plasmodium sp., Eimeria sp., Isospora sp., and Toxoplasma gondii) were isolated. Most prevalent helminths with relatively heavy mean intensity were Strongyloides sp. and Heterakis spumosa, while Plasmodium, Eimeria, and Isospora were the most prevalent protozoan parasites. Generally, intrinsic factors like sex and age had marginal influence on the rate and burden of infection in M. musculus and R. rattus. Although the infection rate and prevalence of zoonotic parasites were low, they were largely recovered in rodents from Ekpoma. This study elucidates the public health implication of the presence of zoonotic parasites in these small mammals.

Toxoplasmosis in Nigeria: the story so far (1950-2016): a review.

Toxoplasmosis is caused by intracellular protozoan parasite, Toxoplasma gondii (Nicolle et Manceaux, 1908). Cats and other felids are the definitive hosts. It could be transmitted to man and animals by consumption of infected undercooked meat and contaminated food items including drinking water. Results of toxoplasmosis epidemiological surveys in animals and humans in South-West, North-West, North-East and North-Central Zones of Nigeria have been reported with greater impact on the health of pregnant women and HIV-infected individuals. Meanwhile, studies in states within the South-South and South-East Zones are relatively scanty or non-existent. Overall, the seroprevalence of human toxoplasmosis in Nigeria is estimated at 32% with the following reports for North-West (32%), North-East (22%), North-Central (24%) and South-West (37%). Information on the genetic diversity of isolates of T. gondii in humans and animals including the role of the environment in transmission and maintenance of the disease are highly needed.

Galleria mellonella is an effective model to study Actinobacillus pleuropneumoniae infection.

Actinobacillus pleuropneumoniae is responsible for swine pleuropneumonia, a respiratory disease that causes significant global economic loss. Its virulence depends on many factors, such as capsular polysaccharides, RTX toxins and iron-acquisition systems. Analysis of virulence may require easy-to-use models that approximate mammalian infection and avoid ethical issues. Here, we investigate the potential use of the wax moth Galleria mellonella as an informative model for A. pleuropneumoniae infection. Genotypically distinct A. pleuropneumoniae clinical isolates were able to kill larvae at 37 °C but had different LD50 values, ranging from 10(4) to 10(7) c.f.u. per larva. The most virulent isolate (1022) was able to persist and replicate within the insect, while the least virulent (780) was rapidly cleared. We observed a decrease in haemocyte concentration, aggregation and DNA damage post-infection with isolate 1022. Melanization points around bacterial cells were observed in the fat body and pericardial tissues of infected G. mellonella, indicating vigorous cell and humoral immune responses close to the larval dorsal vessel. As found in pigs, an A. pleuropneumoniae hfq mutant was significantly attenuated for infection in the G. mellonella model. Additionally, the model could be used to assess the effectiveness of several antimicrobial agents against A. pleuropneumoniae in vivo. G. mellonella is a suitable inexpensive alternative infection model that can be used to study the virulence of A. pleuropneumoniae, as well as assess the effectiveness of antimicrobial agents against this pathogen.

The Antennal Sensilla of Species of the Palpalis Group (Diptera: Glossinidae).

Infection of tsetse fly with trypanosome parasites could be influenced by its ability to locate vertebrate host(s) in the wild. Generally, the antennae of insects are known to bear chemo-sensory organs (sensilla), which are used for host search among other functions. In order to exploit the potentials of tsetse-search behavior, knowledge of sensilla types on the antennae is desirable. In line with this, the dorsal and ventral surfaces of the antennae of Glossina palpalis and Glossina tachinoides (Westwood) were examined under the scanning electron microscope. Results showed that trichoid and chaetica (subtypes I and II) sensilla are present only on the scape and pedicel, while basiconica (subtypes I and II) and sensory pits are seen on the flagella. Microtrichia are present on all the segments of the antennae with Ca II being most abundant. Specifically, in females of G. tachinoides, there is a near-even distribution of Ca I and Ca II on the pedicel while more number of sensory pits was seen on females than males in both species. This study hypothesizes that host-search efficiency could be influenced by the number of olfactory-sensilla types on the antennae, in which case, females present greater potentials.

Comparative analysis of pathogenic organisms in cockroaches from different community settings in Edo State, Nigeria.

Cockroaches are abundant in Nigeria and are seen to harbour an array of pathogens. Environmental and sanitary conditions associated with demographic/socio-economic settings of an area could contribute to the prevalence of disease pathogens in cockroaches. A total of 246 cockroaches (Periplaneta americana) in urban (Benin, n=91), semi-urban (Ekpoma, n=75) and rural (Emuhi, n=70) settings in Edo State, Nigeria were collected within and around households. The external body surfaces and alimentary canal of these cockroaches were screened for bacterial, fungal, and parasitological infections. Bacillus sp. and Escherichia coli were the most common bacteria in cockroaches. However, Enterococcus faecalis could not be isolated in cockroaches trapped from Ekpoma and Emuhi. Aspergillus niger was the most prevalent fungus in Benin and Ekpoma, while Mucor sp. was predominant in Emuhi. Parasitological investigations revealed the preponderance of Ascaris lumbricoides in Benin and Emuhi, while Trichuris trichura was the most predominant in Ekpoma. The prevalence and burden of infection in cockroaches is likely to be a reflection of the sanitary conditions of these areas. Also, cockroaches in these areas making incursions in homes may increase the risk of human infections with these disease agents.

Prevalence of intestinal parasites in animal hosts and potential implications to animal and human health in Edo, Nigeria.

BACKGROUND: Intestinal parasites in livestock cause huge economic setbacks. Moreover, these parasites can threaten human health when also present in companion animals. OBJECTIVES: The study examined the prevalence and burden of intestinal parasites among roaming/migrating animals (goats, sheep, cattle, and dogs) to provide insights into the risk of potential human parasitic infections. METHODS: A total of 1,741 fecal samples from goats (n = 920), sheep (n = 335), cattle (n = 230) and dogs (n = 256) were obtained randomly across 18 local government areas in Edo State, Nigeria. The parasite samples were recovered and identified under a microscope. Molecular tools were used to identify Toxocara spp. RESULTS: Eighteen different parasites were isolated. Among the different groups of parasites observed, nematodes occurred the most, followed by protozoans. Among nematodes, Haemonchus was most prevalent in goats (28.04%) and sheep (29.85%), while Strongyloides (10.86%) and Bunostomum (8.69%) were relatively high in cattle. Strongyloides (3.9%), hookworm (3.9%), and Toxocara (3.12%) were the predominant parasites in dogs. For protozoan parasites, Eimeria was most common in all 4 animal hosts. Several goats (2.39%) and sheep (2.38%) tested positive for Fasciola spp. Molecular analysis confirmed Toxocara canis in dogs for the first time in Nigeria. CONCLUSIONS: The major parasites recovered from these roaming/migrating animals have zoonotic potentials that can threaten human health.

Population genetic analysis of Plasmodium falciparum cell-traversal protein for ookinetes and sporozoite among malaria patients from southern Nigeria.

Plasmodium falciparum immune escape mechanisms affect antigens being prioritized for vaccine design. As a result of the multiple surface antigens the parasite exhibits at different life cycle stages, designing a vaccine that would efficiently boost the immune system in clearing infections has been challenging. The P. falciparum cell-traversal protein for ookinetes and sporozoite (Pfceltos) is instrumental for ookinete traversal of the mosquito midgut and sporozoites invasion of the human liver cells. Pfceltos elicits both humoral and cellular immune response but has been reported with multiple single nucleotide polymorphisms in global isolates. A cross-sectional survey, conducted in southern Nigeria, between January-March 2021 recruited 283 individuals. Of this, 166 demonstrated P. falciparum infections (86 from Cross River and 80 from Edo), 48 (55.8%) while only 36 (45%) were amplified for Pfceltos gene from both sites respectively. Fifty amplified samples were sequenced and analysed for their diversity, polymorphisms and population structure of the gene. The number of segregating sites in Edo State was higher (34) than that of Cross River State. Though nucleotide diversity was higher for Edo compared to Cross River State (θw = 0.02505; π = 0.03993 versus θw = 0.00930; π = 0.01033 respectively), the reverse was the case for haplotype diversity (0.757 versus 0.890 for Edo and Cross River respectively). Of the twelve haplotypes observed from both states, only two (KASLPVEK and NAFLSFEK) were shared, with haplotype prevalence higher in Edo (16% and 36%) than Cross River (8% and 4%). The Tajima's D test was positive for both states, with Fst value showing a strong genetic differentiation (Fst = 0.25599), indicating the occurrence of balancing selection favoring haplotype circulation at a low frequency. The shared haplotypes, low Hst and Fst values presents a challenge to predict the extent of gene flow. High LD values present a grim public health consequence should a Pfceltos-conjugated vaccine be considered for prophylaxis in Nigeria.

Echinococcus granulosus sensu lato in animal intermediate hosts: What is with the organ location?

Organ or tissue tropism/preference in many parasites is essential for their establishment, survival and pathogenesis. In protozoan parasites e.g. Trypanosoma and Plasmodium, tissue tropism is associated with many important aspects such as transmission, treatment, and pathogenesis. In these parasites, tissue tropism is achieved by mechanisms such as sequestration, extravasation, transcellular migration, and vascular permeability. In contrast, little is known about the mechanism behind organ tropism/preference and the potential implication in parasitic metazoans like Echinococcus. Since intraspecies/genetic variation was described for Echinococcus, the organ preference of currently known species and subspecies among animal intermediate hosts remains unclear or perhaps poorly investigated. Here, analysis of 89,359 Echinococcus cysts from different animal intermediate hosts across 47 countries suggests a potential organ distribution pattern in different animal intermediate hosts. For example, E. granulosus s.s. (G1, G3) and E. canadensis (G7) were found more in the liver of sheep and pigs, respectively than in other organs, whereas E. ortleppi and E. canadensis G6 were significantly higher in the lung of cattle and camels, respectively. While the mechanism of organ tropism in Echinococcus and whether it is species/genotype-dependent, host-dependent, or a combination of both is still a subject of future investigations, further and detailed investigation could provide significant information that may be applicable in the diagnosis and treatment of organ-specific cystic echinococcosis or designing host or genotype-specific interventions.

The Burden of Bancroftian Filariasis in Nigeria: A Review.

BACKGROUND: Lymphatic filariasis (LF) is a neglected tropical disease (NTD) vectored by mosquito; and people in rural areas are mostly at risk of infection. Pooling prevalence data across the six geo-political zones of Nigeria is expected to provide a clearer insight into the burden of the disease as this information could guide towards planning eradication programmes. METHODS: Search for pertinent literature was done on Google Scholar, African Journal Online (AJOL) and PubMed databases using relevant keywords. Studies on the prevalence of LF due to Wuchereria bancrofti in Nigeria were selected and reviewed. Prevalence data from the different states were further organized into the six geopolitical zones and analyzed. RESULTS: Of the 36 states in Nigeria, prevalence data were available only for 19 states. Furthermore, in the six geopolitical zones, North-West had the highest disease burden (44 per 10 000) of Years Lived with Disability (YLD), while North-Central (4 per 10 000) had the lowest disease burden. CONCLUSION: Result are largely attributed to the prevailing conditions in the different zones. In view of ensuring a successful control plan and eventual eradication of the disease, a comprehensive national survey in every state should be carried out using more sensitive tools.

Prevalence and distribution of Echinococcus spp. in wild and domestic animals across Africa: A systematic review and meta-analysis.

Cystic echinococcosis (CE), a worldwide zoonosis, is highly prevalent in Africa particularly in northern and eastern Africa where data are more abundant than other regions. However, harmonization of available data through systematic review and meta-analysis may foster improved transboundary cooperation for the control of CE in Africa. Using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, research articles (from 2000 to 2019) were retrieved from ScienceDirect, PubMed, African Journals OnLine and Google Scholar databases. A total of 98 studies of 806,624 animals from 13 countries comprising 264,016 goats, 247,326 sheep, 251,106 cattle, 28,314 camels, 4,764 buffaloes, 2,920 equids, 1,966 pigs, 408 wild boars and 50 Norway rats were available for systematic review and meta-analysis of pooled prevalence including 5,048 dogs, 345 lions, 220 hyenas, 94 wolves and 47 jackals/foxes analysed for Echinococcus infection. In total, 46,869 animals were infected and pooled prevalence of CE in intermediate hosts was highest in camels (17.1%; 95% CI: 12.1-22.8) and lowest in pigs (0.3%; 95% CI: 0.1-0.6). Results also showed uneven species/genotype distribution across the continent such that Echinococcus granulosus sensu stricto (G1, G3) constituted 74.45% of the total isolates from East Africa, E. canadensis (G6/7) accounted for 60.3% and 97.4% in North and West Africa, respectively, while 81.3% of E. ortleppi (G5) were recorded for southern Africa. The comparatively higher prevalence estimates for eastern and northern Africa than other regions indicate where efforts on CE management should now be given greater attention in Africa. Additionally, this study also advocates for better cooperation between countries within the same sub-region and the establishment of joint CE control programmes.

Sustainable Elimination (Zero Cases) of Sleeping Sickness: How Far Are We from Achieving This Goal?

The recent massive reduction in the numbers of fresh Human African Trypanosomiasis (HAT) infection has presented an opportunity for the global elimination of this disease. To prevent a possible resurgence, as was the case after the reduced transmission of the 1960s, surveillance needs to be sustained and the necessary tools for detection and treatment of cases need to be made available at the points of care. In this review, we examine the available resources and make recommendations for improvement to ensure the sustenance of the already achieved gains to keep the trend moving towards elimination.

Cystic echinococcosis in Nigeria: first insight into the genotypes of Echinococcus granulosus in animals.

BACKGROUND: Cystic echinococcosis (CE) is a zoonosis caused by cestodes of Echinococcus granulosus (sensu lato) complex. In Nigeria, reports on the prevalence of CE, although limited, have been found to vary with location and host with higher prevalence and fertility rate observed in camels than other livestock. Until now, information regarding the molecular characteristics, genetic population structure, and genotypes of Echinococcus is lacking. Therefore, this study was aimed at addressing these gaps in knowledge. METHODS: We describe the genetic status of 31 Echinococcus isolates collected from slaughtered livestock (camels, cattle and goats) based on the full-length mitochondrial cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1) genes. RESULTS: The resulting nucleotide sequences via the NCBI BLAST algorithm and Bayesian phylogeny of cox1 and cox1-nad1 genes using MrBayes v.3.1.2 showed that all isolates were clearly E. canadensis (G6/G7) and were 99-100% identical to previously reported G6/G7 haplotypes across Europe, Asia, North and East Africa. CONCLUSIONS: Although, the G1 genotype is believed to be responsible for the majority of global CE burden, reports from a number of West African countries including Nigeria suggest that E. canadensis G6/G7 genotype could be the major causative agent of CE in the subregion. This study provides for the first time insight into the genetic population structure of Echinococcus species as well as implications for CE control in Nigeria.

Entomological assessment of yellow fever-epidemic risk indices in Benue State, Nigeria, 2010-2011.

Yellow fever (YF) is a vector-borne disease affecting humans and non-human primates in tropical areas. In the past, there have been pockets of YF outbreaks in Nigeria that resulted in preventable deaths. Surveillance efforts towards avoiding another outbreak have been put in place with the aim of early detection and control. However, risk indices relating to the density of immature YF-mosquito vectors are given little consideration even though it is the first step in curbing a possible outbreak. Immature collections from 1538 houses in Ega, Oju, Otukpoicho and Otukpo in Benue State were carried out in 2010 and 2011. Risk indices such as house index (HI), container index (CI) and Breteau index (BI) were estimated. Molecular detection of YF was carried out on randomly selected Aedes larvae and pupae. Overall, 431,381 mosquitoes were collected in and around house premises. Thirteen species were identified: Ae. aegypti (Linneaus), Ae. africanus (Theobald), Ae. albopictus (Skuse), Ae. cumminsii (Theobald), Ae. luteocephalus (Newstead), Ae. simpsoni s.l. (Theobald), Ae. vittatus (Bigot), Anopheles gambiae Giles, An. nili (Theobald), Cx. nebulosus Theobald, Culex quinquefasciatus Say, Lutzia tigripes (Grandpre and Charmoy) and Toxorhynchites brevipalpis Theobald. The HI, CI and BI for Ae. aegypti were high in all the study locations, but low for Ae. lueteocephalus except in Ega. With 50 immature Aedes mosquitoes screened across locations, only Ae. aegypti from Ega were positive for YF. This study places Ega on a high alert of an impending YF outbreak. Thus, urgent steps to clear this area of potential mosquito sites are highly recommended.

Molecular identification of different trypanosome species and subspecies in tsetse flies of northern Nigeria.

BACKGROUND: Animal African Trypanosomiasis (AAT) is caused by several species of trypanosomes including Trypanosoma congolense, T. vivax, T. godfreyi, T. simiae and T. brucei. Two of the subspecies of T. brucei also cause Human African Trypanosomiasis. Although some of them can be mechanically transmitted by biting flies; these trypanosomes are all transmitted by tsetse flies which are the cyclical vectors of Trypanosoma congolense, T. godfreyi, T. simiae and T. brucei. We present here the first report assessing the prevalence of trypanosomes in tsetse flies in Nigeria using molecular tools. METHODS: 488 tsetse flies of three species, Glossina palpalis palpalis, G. tachinoides and G. morsitans submorsitans were collected from Wuya, Niger State and Yankari National Park, Bauchi State in 2012. Trypanosomes were detected and identified using an ITS1 PCR assay on DNA purified from the 'head plus proboscis' (H + P) and abdomen (ABD) parts of each fly. RESULTS: T. vivax and T. congolense Savannah were the major parasites detected. Trypanosomes prevalence was 7.1 % in G. p. palpalis, 11.9 % in G. tachinoides and 13.5 % in G. m. submorsitans. Prevalences of T. congolense Savannah ranged from 2.5 to 6.7 % and of T. vivax were approximately 4.5 %. Trypanosoma congolense Forest, T. godfreyi and T. simiae were also detected in the site of Yankari. The main biological and ecological determinants of trypanosome prevalence were the fly sex, with more trypanosomes found in females than males, and the site, with T. congolense subspp. being more abundant in Yankari than in Wuya. As expected, the trypanosome species diversity was higher in Yankari National Park than in the more agricultural site of Wuya where vertebrate host species diversity is lower. CONCLUSIONS: Our results show that T. congolense Savannah and T. vivax are the main species of parasite potentially causing AAT in the two study sites and that Yankari National Park is a potential reservoir of trypanosomes both in terms of parasite abundance and species diversity.

Cluster of differentiation expressions among Nigerians with Ascaris lumbricoides infection.

Clusters of differentiation (CDs) are membrane proteins expressed on cells of the immune system and are associated with parasitic infection. Most of the work on CD expressions to helminth infection has mainly been on mouse model. Thus there is a dearth of information on the influence of Ascaris lumbricoides to CD expressions in human blood. White blood cell (WBC), eosinophil and platelet numbers were estimated alongside their CD14, CD40 and CD130 concentrations in A. lumbricoides-infected human subjects. Similarly, serum CD levels in relation to Ascaris-infected and helminth co-infected with healthy controls were estimated. The relationship between Ascaris load and CD profile was also shown. Our data indicated that >6 eosinophil-counts group expressed raised mean level of CD14 with a highly depressed mean CD40. Furthermore, mean CD40 for individuals with low platelet count was highly depressed. Additional analysis of infected vs control and the correlation of CD levels with parasite load showed null effect of A. lumbricoides on CD14 and CD40 expressions. Meanwhile, CD130 was raised as platelet number and parasite load increased. Thus the involvement of CD130 in the immuno-pathology of Ascariasis is likely. CD130 could therefore be a marker of infection and a potential target for improved anthelminthic therapy.

Chemokines responses to Plasmodium falciparum malaria and co-infections among rural Cameroonians.

Malaria remains the major cause of disease morbidity and mortality in sub-Saharan Africa with complex immune responses associated with disease outcomes. Symptoms associated with severe malaria have generally shown chemokine upregulation but little is known of responses to uncomplicated malaria. Eight villages in central Cameroon of 1045 volunteers were screened. Among these, malaria-positive individuals with some healthy controls were selected for chemokine analysis using Enzyme-Linked Immunosorbent Assay (ELISA) kits. Depressed serum levels of CXCL5 and raised CCL28 were observed in malarial positives when compared with healthy controls. The mean concentration of CXCL11 was higher in symptomatic than asymptomatic group, while CCL28 was lower in symptomatic individuals. Lower chemokine levels were associated with symptoms of uncomplicated malaria except for CXCL11 which was upregulated among fever-positive group. The mean CXCL5 level was higher in malaria sole infection than co-infections with HIV and Loa loa. Also, there was a raised mean level of malaria+HIV co-infection for CXCL9. This study hypothesises a situation where depressed chemokines in the face of clinical presentations could indicate an attempt by the immune system in preventing a progression process from uncomplicated to complicated outcomes with CXCL11 being identified as possible biomarker for malarial fever.