Cytochrome b Drug Resistance Mutation Decreases Babesia Fitness in the Tick Stages But Not the Mammalian Erythrocytic Cycle.

Human babesiosis is an emerging tick-borne malaria-like illness caused by Babesia parasites following their development in erythrocytes. Here, we show that a mutation in the Babesia microti mitochondrial cytochrome b (Cytb) that confers resistance to the antibabesial drug ELQ-502 decreases parasite fitness in the arthropod vector. Interestingly, whereas the mutant allele does not affect B. microti fitness during the mammalian blood phase of the parasite life cycle and is genetically stable as parasite burden increases, ELQ-502-resistant mutant parasites developing in the tick vector are genetically unstable with a high rate of the wild-type allele emerging during the nymphal stage. Furthermore, we show that B. microti parasites with this mutation are transmitted from the tick to the host, raising the possibility that the frequency of Cytb resistance mutations may be decreased by passage through the tick vector, but could persist in the environment if present when ticks feed.

Babesiosis as a potential threat for bovine production in China.

Babesiosis is a tick-borne disease with global impact caused by parasites of the phylum Apicomplexa, genus Babesia. Typically, acute bovine babesiosis (BB) is characterized by fever, anemia, hemoglobinuria, and high mortality. Surviving animals remain persistently infected and become reservoirs for parasite transmission. Bovids in China can be infected by one or more Babesia species endemic to the country, including B. bovis, B. bigemina, B. orientalis, B. ovata, B. major, B. motasi, B. U sp. Kashi and B. venatorum. The latter may pose a zoonotic risk. Occurrence of this wide diversity of Babesia species in China may be due to a combination of favorable ecological factors, such as the presence of multiple tick vectors, including Rhipicephalus and Hyalomma, the coexistence of susceptible bovid species, such as domestic cattle, yaks, and water buffalo, and the lack of efficient measures of tick control. BB is currently widespread in several regions of the country and a limiting factor for cattle production. While some areas appear to have enzootic stability, others have considerable cattle mortality. Research is needed to devise solutions to the challenges posed by uncontrolled BB. Critical research gaps include risk assessment for cattle residing in endemic areas, understanding factors involved in endemic stability, evaluation of parasite diversity and pathogenicity of regional Babesia species, and estimation of whether and how BB should be controlled in China. Research should allow the design of comprehensive interventions to improve cattle production, diminish the risk of human infections, and increase the availability of affordable animal protein for human consumption in China and worldwide. In this review, we describe the current state of BB with reference to the diversity of hosts, vectors, and parasite species in China. We also discuss the unique risks and knowledge gaps that should be taken into consideration for future Babesia research and control strategies.

Emergence of Babesia conradae infection in coyote-hunting Greyhounds in Oklahoma, USA.

BACKGROUND: Babesia species are intraerythrocytic Apicomplexan parasites that infect a wide range of vertebrate hosts. These pathogens are typically transmitted either by tick vectors or by direct blood-to-blood contact, and may cause life-threatening clinical disease, such as thrombocytopenia, hemolytic anemia and acute renal failure, in canine hosts. While Babesia vogeli and Babesia gibsoni infections have both been reported in Oklahoma, reports of Babesia conradae infections have been limited to California. METHODS: Four separate kennels of coyote-hunting dogs were identified in Oklahoma after the kennels had consulted with Oklahoma State University Boren Veterinary Medical Teaching Hospital (antemortem cases) or the Oklahoma Animal Disease Diagnostic Lab (postmortem cases). Upon owner consent, every accessible dog from each of the four kennels was briefly examined for ectoparasites, particularly ticks, and whole blood samples were collected in EDTA tubes. Clinically ill dogs were examined by a practicing veterinarian, and clinical signs included anorexia, vomiting, lethargy, fever and anemia. DNA was extracted from each blood sample, and a nested PCR was performed using general apicomplexan primers for the partial 18S rRNA gene. PCR products were electrophoresed in agarose matrix, and appropriately sized amplicons were sequenced. Sequences were compared to reference 18S rRNA gene sequences available in GenBank, and samples with > 98% homology to B. conradae (GenBank: AF158702) were considered positive. Babesia conradae-positive dogs were then treated with atovaquone (13.5 mg/kg three times per day) and azithromycin (10 mg/kg once daily) for 10 days and retested at 30 and 60 days post-treatment by PCR. RESULTS: Of 40 dogs tested, 15 (37.5%) were positive for B. conradae with 98-99% sequence homology to B. conradae from California. All positive cases were coyote-hunting Greyhounds. Ectoparasites were not identified on any of the dogs at the time of blood collection. Treatment of clinically ill dogs with atovaquone and azithromycin resulted in complete clinical recovery in all treated dogs with negative follow-up PCR at 30 and 60 days post-treatment. CONCLUSIONS: Collectively, this study (i) documents the occurrence of B. conradae in Oklahoma, (ii) highlights this pathogen as a differential to be considered when clinical signs are present, (iii) supports the use of atovaquone and azithromycin as effective treatment in these cases and (iv) demonstrates chronic subclinical carrier dogs serving as potential reservoirs of B. conradae infection to naïve dogs.

Differential expression of calcium-dependent protein kinase 4, tubulin tyrosine ligase, and methyltransferase by xanthurenic acid-induced Babesia bovis sexual stages.

BACKGROUND: Babesia bovis is one of the most significant tick-transmitted pathogens of cattle worldwide. Babesia bovis parasites have a complex lifecycle, including development within the mammalian host and tick vector. Each life stage has developmental forms that differ in morphology and metabolism. Differentiation between these forms is highly regulated in response to changes in the parasite's environment. Understanding the mechanisms by which Babesia parasites respond to environmental changes and the transmission cycle through the biological vector is critically important for developing bovine babesiosis control strategies. RESULTS: In this study, we induced B. bovis sexual stages in vitro using xanthurenic acid and documented changes in morphology and gene expression. In vitro induced B. bovis sexual stages displayed distinctive protrusive structures and surface ruffles. We also demonstrated the upregulation of B. bovis calcium-dependent protein kinase 4 (cdpk4), tubulin-tyrosine ligase (ttl), and methyltransferase (mt) genes by in vitro induced sexual stages and during parasite development within tick midguts. CONCLUSIONS: Similar to other apicomplexan parasites, it is likely that B. bovis upregulated genes play a vital role in sexual reproduction and parasite transmission. Herein, we document the upregulation of cdpk4, ttl, and mt genes by both B. bovis in vitro induced sexual stages and parasites developing in the tick vector. Understanding the parasite's biology and identifying target genes essential for sexual reproduction will enable the production of non-transmissible live vaccines to control bovine babesiosis.

Risk of transfusion-transmitted Babesia microti in Canada.

BACKGROUND: Babesia microti has gained a foothold in Canada as tick vectors become established in broader geographic areas. B. microti infection is associated with mild or no symptoms in healthy individuals but is transfusion-transmissible and can be fatal in immunocompromised individuals. This is the first estimate of clinically significant transfusion-transmitted babesiosis (TTB) risk in Canada. STUDY DESIGN AND METHODS: The proportion of B. microti-antibody (AB)/nucleic acid amplification test (NAT)-positive whole blood donations was estimated at 5.5% of the proportion of the general population with reported Lyme Disease (also tick-borne) based on US data. Monte Carlo simulation estimated the number and proportion of infectious red cell units for three scenarios: base, localized incidence (risk in Manitoba only), and donor study informed (prevalence from donor data). The model simulated 1,029,800 donations repeated 100,000 times for each. RESULTS: In the base scenario 0.5 (0.01, 1.75), B. microti-NAT-positive donations would be expected per year, with 0.08 (0, 0.38) recipients suffering clinically significant TTB (1 every 12.5 years). In the localized incidence scenario, there were 0.21(0, 0.7) B. microti-NAT-positive donations, with 0.04 (0, 0.14) recipient infections (about 1 every 25 years). In the donor study informed scenario, there were 4.6 (0.3, 15.8) B. microti-NAT-positive donations expected, and 0.81 (0.05, 3.14) clinically significant TTB cases per year. DISCUSSION: The likelihood of clinically relevant TTB is low. Testing would have very little utility in Canada at this time. Ongoing pathogen surveillance in tick vectors is important as B. microti prevalence appears to be slowly increasing in Canada.

Monitoring the expansion of Dermacentor reticulatus and occurrence of canine babesiosis in Poland in 2016-2018.

BACKGROUND: The significance of tick-borne diseases has increased considerably in recent years. Because of the unique distribution of the tick species Dermacentor reticulatus in Poland, comprising two expanding populations, Eastern and Western that are separated by a Dermacentor-free zone, it is important to conduct studies on the process of tick expansion and emergence of canine babesiosis. The main aim of the current study was to monitor the expansion of D. reticulatus populations from spring 2016 to autumn 2018 to determine (1) the actual geographical range of this tick species, and (2) and the seasonal/annual shift in range limits and changes in distance between Western and Eastern populations of ticks (the size of the non-endemic area). METHODS: Ticks were collected in spring/autumn during a 3-year study. From each season and year at least three pairs of sites from the Western and Eastern populations were selected. Then the mean distance between paired sites was calculated for each season and year. We collected and analyzed data from veterinary clinics on the number of canine babesiosis cases treated in the clinic during a whole year (2018). RESULTS: Accordingly, further expansion of the two D. reticulatus populations was recorded, mainly along river basins. Marked colonization of the gap zone was observed, with a mean annual shift in the range of 2.5-10 km and a steadily decreasing distance between the two tick populations. The occurrence of babesiosis in different regions revealed low numbers of cases in Western Poland (19 cases/year) and the gap area (only 7 cases/year) and high incidence (up to 250 cases/1000 dogs) and fatality (total 3.65%) in Central and Eastern Poland. Strong associations were found geographically between tick and babesiosis occurrence and temporally in the seasonal patterns of occurrence of ticks and outbreaks of babesiosis. CONCLUSIONS: We documented the shift in range limits and continued process of colonization of the gap zone accompanied by the emergence of canine babesiosis in the Eastern expansion zone. Updated maps of the distribution of ticks and occurrence of babesiosis in different regions of Poland have allowed us to predict of the emergence of pathogens vectored by D. reticulatus. Incidence (per 1000 dogs) of canine babesiosis in veterinary clinics by current range of D. reticulatus.

Three Babesia species in Ixodes ricinus ticks from migratory birds in Sweden.

BACKGROUND: Migratory birds can cross geographical and environmental barriers and are thereby able to facilitate transmission of tick-borne pathogens both as carriers of infected ticks and as reservoirs of pathogenic microorganisms. Ixodes ricinus is one of the most abundant tick species in the Northern Hemisphere and a main vector of several Babesia species, some which pose a potential threat to human and animal health. At present only two cases of overt babesiosis in humans have so far been reported in Sweden. To better understand the potential role of birds as disseminators of zoonotic Babesia protozoan parasites, we investigated the presence of Babesia species in ticks removed from migratory birds. METHODS: Ticks were collected from birds captured at Ottenby Bird Observatory, south-eastern Sweden, from March to November 2009. Ticks were molecularly identified to species, and morphologically to developmental stage, and the presence of Babesia protozoan parasites was determined by real-time PCR. RESULTS: In total, 4601 migratory birds of 65 species were examined for tick infestation. Ticks removed from these birds have previously been investigated for the presence of Borrelia bacteria and the tick-borne encephalitis virus. In the present study, a total of 1102 ticks were available for molecular analysis of Babesia protozoan parasites. We found that 2.4% of the ticks examined, all I. ricinus, were positive for mammal-associated Babesia species. Out of all Babesia-positive samples, Babesia venatorum was the most prevalent (58%) species, followed by Babesia microti (38%) and Babesia capreoli (4.0%). B. venatorum and B. capreoli were detected in I. ricinus larvae, whereas B. microti was only present in I. ricinus nymphs. This supports the view that the two first-mentioned species are vertically (transovarially) transmitted in the tick population, in contrast to B. microti. The largest number of Babesia-infected ticks was removed from the common redstart (Phoenicurus phoenicurus) and European robin (Erithacus rubecula). CONCLUSIONS: This study reveals that Babesia protozoan parasites are present in ticks infesting migratory birds in south-eastern Sweden, which could potentially lead to the dissemination of these tick-borne microorganisms into new areas, thus posing a threat to humans and other mammals.

Update on prevalence and distribution pattern of tick-borne diseases among humans in India: a review.

In the present scenario, tick-borne diseases (TBDs) are well known for their negative impacts on humans as well as animal health in India. The reason lies in their increased incidences due to global warming, environmental and ecological changes, and availability of suitable habitats. On a global basis, they are now considered a serious threat to human as well as livestock health. The major tick-borne diseases in India include Kyasanur forest disease (KFD), Crimean-congo hemorrhagic fever (CCHF), Lyme disease (LD), Q fever (also known as coxiellosis), and Rickettsial infections. In recent years, other tick-borne diseases such as Babesiosis, Ganjam virus (GANV), and Bhanja virus (BHAV) infections have also been reported in India. The purpose of this paper is to review the history and the current state of knowledge of tick-borne diseases in the country. The conclusion of this review is extending the requirement of greater efforts in research and government management for the diagnosis and treatment and as well as prevention of these diseases so that tick-borne disease burden should be minimizing in India.

Coinfection of Ixodes scapularis (Acari: Ixodidae) Nymphs With Babesia spp. (Piroplasmida: Babesiidae) and Borrelia burgdorferi (Spirochaetales: Spirochaetaceae) in Wisconsin.

Borrelia burgdorferi, the spirochete that causes Lyme disease, is endemic and widespread in Wisconsin. Research in the northeastern United States has revealed a positive association between Babesia microti, the main pathogen that causes babesiosis in humans, and Bo. burgdorferi in humans and in ticks. This study was conducted to examine associations between the disease agents in the Upper midwestern United States. Ixodes scapularis Say nymphs (N = 2,858) collected between 2015 and 2017 from nine locations in Wisconsin were tested for Babesia spp. and Borrelia spp. using real-time PCR. Two species of Babesia were detected; Ba. microti and Babesia odocoilei (a parasite of members of the family Cervidae). Prevalence of infection at the nine locations ranged from 0 to 13% for Ba. microti, 11 to 31% for Bo. burgdorferi sensu stricto, and 5.7 to 26% for Ba. odocoilei. Coinfection of nymphs with Bo. burgdorferi and Ba. odocoilei was detected in eight of the nine locations and significant positive associations were observed in two of the eight locations. The prevalence of nymphal coinfection with both and Bo. burgdorferi and Ba. microti ranged from 0.81 to 6.5%. These two pathogens were significantly positively associated in one of the five locations where both pathogens were detected. In the other four locations, the observed prevalence of coinfection was higher than expected in all but one site-year. Clinics and healthcare providers should be aware of the association between Ba. microti and Bo. burgdorferi pathogens when treating patients who report tick bites.

Biosurveillance and Research Needs Involving Area-Wide Systematic Active Sampling to Enhance Integrated Cattle Fever Tick (Ixodida: Ixodidae) Eradication.

The one-host cattle fever tick, Rhipicephalus (Boophilus) annulatus (Say), and southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini), are important ectoparasitic pests of cattle, Bos taurus L., mostly for transmitting the causal agents of bovine babesiosis. Bovine babesiosis inflicted substantial cattle production losses in the United States before the vectors were eliminated by 1943, with the exception of a Permanent Quarantine Zone in South Texas, a buffer along the Mexico border where the invasive ixodids remain. As suitable hosts, infested white-tailed deer and nilgai antelope populations disperse R. annulatus and R. microplus, which increases the risk for emergence of bovine babesiosis in the United States. A R. microplus incursion first detected in 2016 on the South Texas coastal plain wildlife corridor involved infestations on cattle, nilgai antelope, white-tailed deer, and vegetation. Efforts at passive sampling of Rhipicephalus (Boophilus) spp. on hosts are concentrated in the Permanent Quarantine Zone. Hence, a knowledge gap exists on the full extent of the recent incursions. Area-wide, systematic, active sampling and supportive research, involving the Permanent Quarantine Zone, Temporary Quarantine Zone, most of the coastal plain, and other parts of Texas outside of the quarantine zones, are needed to bridge the knowledge gap. Herein, we provide research perspectives and rationale to develop and implement systematic active sampling that will provide an increasingly accurate assessment of Rhipicephalus (Boophilus) spp. distribution in Texas. We suggest that this is essential to advance integrated vector-borne animal disease eradication approaches for keeping cattle free of bovine babesiosis.

Assessment of Babesia bovis 6cys A and 6cys B as components of transmission blocking vaccines for babesiosis.

BACKGROUND: Babesia bovis reproduces sexually in the gut of its tick vector Rhipicephalus microplus, which involves expression of 6cys A and 6cys B proteins. Members of the widely conserved 6cys superfamily are candidates for transmission blocking vaccines (TBV), but intricacies in the immunogenicity of the 6cys proteins in the related Plasmodium parasites required the identification of transmission blocking domains in these molecules for vaccine design. Hereby, the immunogenic efficacy of recombinant (r) B. bovis 6cys A and B proteins as a TBV formulation was studied. METHODS: The immunogenicity of r6cys A and 6cys B proteins expressed in a eukaryotic system was evaluated in a cattle immunization trial (3 immunized and 3 control calves). A B. bovis sexual stage induction in vitro inhibition assay to assess the ability of antibodies to block the production of sexual forms by the parasite was developed. RESULTS: Immunized cattle generated antibodies against r6cys A and r6cys B that were unable to block sexual reproduction of the parasite in ticks. Additionally, these antibodies also failed in recognizing native 6cys A and 6cys B and peptides representing 6cys A and 6cys B functional domains and in inhibiting the development of sexual forms in an in vitro induction system. In contrast, rabbit antibodies generated against synthetic peptides representing predicted B-cell epitopes of 6cys A and 6cys B recognized recombinant and native forms of both 6cys proteins as well as peptides representing 6cys A and 6cys B functional domains and were able to neutralize development of sexual forms of the parasite in vitro. CONCLUSIONS: These data, combined with similar work performed on Plasmodium 6cys proteins, indicate that an effective 6cys protein-based TBV against B. bovis will require identifying and targeting selected regions of proteins containing epitopes able to reduce transmission.

Molecular evidence indicts Haemaphysalis leachi (Acari: Ixodidae) as the vector of Babesia rossi in dogs in Nigeria, West Africa.

Babesia rossi is the most pathogenic among the large canine babesias and it is the major cause of canine babesisosis in Nigeria. In South Africa it is transmitted by Haemaphysalis elliptica however, its putative vector in Nigeria where Rhipicephalus sanguineus is the most prevalent tick on dogs compared to Haemaphysalis species has not been ascertained. The incongruity between tick distribution and the frequent detection of B. rossi in Nigeria motivated this investigation to identify the local vector(s) of B. rossi. A total of 3805 ticks were collected from 363 naturally infested dogs from different parts of Nigeria. Of these numbers, 758 engorged female ticks; Rh. sanguineus (n = 660) and H. leachi (n = 98) were incubated for oviposition and hatching. After the completion of egg laying, Rh. sanguineus (n = 69) and H. leachi (n = 24) and their resulting progenies were screened for the presence of B. rossi DNA using a nested PCR targeting the 693 bp of the 18S rRNA gene of Babesia spp. Amplification and sequencing of B. rossi DNA was successful in the adults of H. leachi and their resulting egg and larval progenies but not in the adult Rh. sanguineus and progenies. The B. rossi DNA sequences from the H. leachi and their progenies have 99-100 % identity to each other and 98-99 % identical to sequences of B. rossi in GenBank (GenBank: MH143395.1), thus confirming transovarian passage. This evidence confirms for the first time following the reclassification of H. leachi to H. elliptica in South Africa the role of H. leachi in the transmission of B. rossi in dogs in Nigeria.

Impact of Babesia microti infection on the initiation and course of pregnancy in BALB/c mice.

BACKGROUND: Protozoa in the genus Babesia are transmitted to humans through tick bites and cause babesiosis, a malaria-like illness. Vertical transmission of Babesia spp. has been reported in mammals; however, the exact timing and mechanisms involved are not currently known. The aims of this study were to evaluate the success of vertical transmission of B. microti in female mice infected before pregnancy (mated during the acute or chronic phases of Babesia infection) and that of pregnant mice infected during early and advanced pregnancy; to evaluate the possible influence of pregnancy on the course of parasite infections (parasitaemia); and to assess pathological changes induced by parasitic infection. METHODS: The first set of experiments involved two groups of female mice infected with B. microti before mating, and inseminated on the 7th day and after the 40th day post infection. A second set of experiments involved female mice infected with B. microti during pregnancy, on the 4th and 12th days of pregnancy. Blood smears and PCR targeting the 559 bp 18S rRNA gene fragment were used for the detection of B. microti. Pathology was assessed histologically. RESULTS: Successful development of pregnancy was recorded only in females mated during the chronic phase of infection. The success of vertical transmission of B. microti in this group was 63%. No evidence of pregnancy was found in females mated during the acute phase of infection or on the 4th day of pregnancy. In the group infected on the 12th day of pregnancy, numerous complications including loss of pregnancy and stillbirths were recorded. During the acute phase of infection, parasitaemia was lower in pregnant females in comparison to infected, non-pregnant control females. CONCLUSIONS: Acute B. microti infection prevents the initiation of pregnancy and embryonic development if it occurs during the first trimester, and causes severe complications in foetal BALB/c mice in the second and third trimesters of pregnancy. Chronic B. microti infection has no detrimental impact on the initiation and development of pregnancy, but results in congenital infection of the offspring. Further study is required to determine the extent to which maternal anti-babesial immune responses contribute to compromise pregnancy in the murine model of congenital Babesia infection.

Effects of white-tailed deer habitat use preferences on southern cattle fever tick eradication: simulating impact on "pasture vacation" strategies.

BACKGROUND: Rhipicephalus (Boophilus) annulatus and Rhipicephalus (Boophilus) microplus (southern cattle fever tick; SCFT), collectively known as cattle-fever ticks (CFTs), are vectors of protozoal parasites (Babesia bigemina and Babesia bovis) that cause bovine babesiosis (also known as cattle fever). One traditional strategy for CFT eradication involves the implementation of a "pasture vacation," which involves removing cattle (Bos taurus) from an infested pasture for an extended period of time. However, vacated pastures are often inhabited by wildlife hosts, such as white-tailed deer (WTD; Odocoileus virginianus), which can serve as alternate hosts for questing CFTs. We hypothesized that the distribution of host-seeking larvae among habitat types post-pasture vacation would reflect habitat use patterns of WTD, and in turn, affect the subsequent rate of pasture infestation by CFT. METHODS: We adapted a spatially explicit, individual-based model to simulate interactions among SCFT, cattle, and WTD as a tool to investigate the potential effects of WTD habitat use preferences on the efficacy of a pasture vacation. We parameterized the model to represent conditions typical of rangelands in south Texas, USA, simulated a 1-year pasture vacation under different assumptions regarding WTD habitat use preferences, and summarized effects on efficacy through (1) time post-vacation to reach 100% of pre-vacation densities of host-seeking larvae, and (2) the ecological conditions that resulted in the lowest host-seeking larval densities following pasture vacation. RESULTS: Larval densities at the landscape scale varied seasonally in a similar manner over the entire simulation period, regardless of WTD habitat use preferences. Following the removal of cattle, larval densities declined sharply to < 100 larvae/ha. Following the return of cattle, larval densities increased to > 60% of pre-vacation densities ≈ 21 weeks post-vacation, and reached pre-vacation levels in less than a year. Trends in larval densities in different habitat types paralleled those at the landscape scale over the entire simulation period, but differed quantitatively from one another during the pasture vacation. Relative larval densities (highest to lowest) shifted from (1) wood/shrub, (2) grass, (3) mixed-brush during the pre-vacation period to (1) mixed-brush, (2) wood/shrub, (3) grass or (1) wood/shrub, (2) mixed-brush, (3) grass during the post-vacation period, depending on WTD habitat use preferences. CONCLUSIONS: By monitoring WTD-driven shifts in distributions of SCFT host-seeking larvae among habitat types during simulated pasture vacation experiments, we were able to identify potential SCFT refugia from which recrudescence of infestations could originate. Such information could inform timely applications of acaricides to specific refugia habitats immediately prior to the termination of pasture vacations.

Prevalence of tick-transmitted pathogens in cattle reveals that Theileria parva, Babesia bigemina and Anaplasma marginale are endemic in Burundi.

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.

Vertical Transmission: A Vector-Independent Transmission Pathway of Babesia microti in the Natural Reservoir Host Peromyscus leucopus.

BACKGROUND: Babesia microti, a malaria-like pathogen, is increasing in mammal and human populations in endemic areas and is unlikely to be the sole result of horizontal pathogen transmission. METHODS: Peromyscus leucopus mice, natural reservoir hosts, were infected via Ixodes scapularis nymphs. Infected parental females (n = 6) produced F1 offspring (n = 36) that were screened for B. microti using quantitative PCR. Xenodiagnostic larvae were fed on infected offspring to determine horizontal transmission and pathogen viability. Fifty engorged larvae were screened; the rest were allowed to molt and then screened to determine transstadial transmission. Infected F1 generation offspring were placed in breeding groups, producing 34 F2 offspring and screened for B. microti infection. Chronic infection was monitored in parental females since time of initial vector infection. RESULTS: Vertical transmission of B. microti was 74% efficient in offspring born in the first 6 months. Horizontal transmission occurred in larvae (61% prevalence) and molted nymphs (58% prevalence); these nymphs were able to infect susceptible hosts. F2 generation offspring infection prevalence was 38%. Chronic infection persisted for 1 year in some adults. CONCLUSIONS: These results demonstrate that vertical transmission is an important nonvector-mediated pathway of B. microti transmission in the natural reservoir host.

A framework for signaling throughout the life cycle of Babesia species.

Babesia species are tick-borne intracellular parasites that infect the red blood cells of their mammalian host, leading to severe or fatal disease. Babesia spp. infect a wide range of mammalian species and cause a significant economic burden globally, predominantly through disease in cattle. Several Babesia spp. are increasingly being recognized as zoonotic pathogens of humans. Babesia spp. have complex life cycles involving multiple stages in the tick and the mammalian host. The parasite utilizes complex signaling pathways during replication, egress, and invasion in each of these stages. They must also rapidly respond to their environment when switching between the mammalian and tick stages. This review will focus on the signaling pathways and environmental stimuli that Babesia spp. utilize in the bloodstream and for transmission to the tick, with an emphasis on the role of phosphorylation- and calcium-based signaling during egress and invasion. The expanding availability of in vitro and in vivo culture systems, genomes, transcriptomes, and transgenic systems available for a range of Babesia spp. should encourage further biological and translational studies of these ubiquitous parasites.

High prevalence of Babesia microti in small mammals in Beijing.

BACKGROUND: Babesiosis is an emerging tick-borne zoonotic infectious disease. Babesia microti is responsible for most cases of human babesiosis globally. It is important to investigate the prevalence of B. microti in the mammalian host population of a specific region in order to elucidate mechanisms of pathogen transmission and to define geographic areas where humans face the greatest risk of exposure. The aim of this study is to understand the prevalence and genotypes of B. microti in the small mammals that are found in Beijing, China. METHODS: We trapped small mammals from all of the 16 urban, suburban, and outer suburban districts of Beijing during the years 2014, 2017 and 2018. Genomic DNA was extracted from the heart tissues individually and the Babesia 18S rRNA gene was detected by PCR. The genotypes of B. microti were identified based on sequence alignments and phylogenetic analysis. The morphology of the parasites was observed under light microscopy. The risk factors were analyzed statistically based on both univariate analyses and multivariate logistic regression. RESULTS: A total of 1391 small mammals were collected. Positive infection of B. microti was detected in 12.1% (168/1391) of small mammals from 15 out of the 16 districts. Both Kobe-type and U.S.-type B. microti, accounting for 9.5% and 2.7%, respectively, were identified. Classic diverse morphologic forms of B. microti were observed. Specific types of ecological habitats including shrub areas, broad-leaved forest, and cropland were revealed to be risk factors associated with B. microti infection. CONCLUSIONS: This study demonstrated the wide prevalence of B. microti infection in eight species of small mammals in Beijing, with Kobe-type more prevalent than U.S.-type. This study provides fundamental information for the development of informed prevention and control measures by public health authorities; the data gathered indicates a need for further monitoring of both clinical diseases in individuals presenting with babesiosis-like symptoms, as well as the infection status of ticks in high risk areas.