Development and evaluation of a nested PCR based on spherical body protein 2 gene for the diagnosis of Babesia bovis infection

Tick-borne Pathogen Detection and Its Association with Alterations in Packed Cell Volume of Dairy Cattle in Thailand

Tick-borne diseases (TBDs) massively impact bovine production. In endemic countries, animals are often subclinically infected, showing no signs of the illness. Anemia is a hallmark of TBDs, but there is inadequate information on its presence in infected Thai cattle. In the present study, 265 cattle from four provinces in Thailand were surveyed to identify tick-borne pathogens (TBPs) and to evaluate the changes in the packed cell volume (PCV) values associated with detection. Microscopy and polymerase chain reaction (PCR) were also compared for TBP detection. Babesia/Theileria/Hepatozoon was detected in 33.58% (89/265) of the cattle samples. Specifically, Babesia bovis (9/265), B. bigemina (12/265), Theileria orientalis (62/265), and Anaplasma marginale (50/265) were identified using species-specific assays. Significant decreases in the mean PCV levels were observed in cattle that were positive for at least one TBP (p < 0.001), Babesia/Theileria/Hepatozoon (p < 0.001), T. orientalis (p < 0.001), and A. marginale (p = 0.049). The results of PCR and microscopy for the detection of TBPs suggested slight and fair agreement between the two detection tools. The present findings contribute to a better understanding of TBDs in the field and shall facilitate the formulation of effective control for TBDs in Thailand.

Molecular characterization and genetic diversity of Babesia bovis and Babesia bigemina of cattle in Thailand

Babesia bovis and B. bigemina are the most common tick-borne parasites that cause bovine babesiosis which effects livestock production, leading to economic losses in tropical and subtropical areas of the world. The aims of this study were to determine the molecular detection, genetic diversity and antigenicity prediction of B. bovis based on spherical body protein 2 (sbp-2) gene and B. bigemina based on rhoptry-associated protein 1a (rap-1a) gene in cattle in Thailand. By PCR assay, the molecular detection of B. bovis and B. bigemina infection revealed levels of 2.58% (4/155) and 5.80% (9/155), respectively. The phylograms showed that B. bovis sbp-2 and B. bigemina rap-1a sequences displayed 5 and 3 clades with similarity ranging between 85.53 to 100% and 98.28 to 100%, respectively, when compared within Thailand strain. Diversity analysis of sbp-2 and rap-1a sequences showed 18 and 4 haplotypes, respectively. The entropy analysis illustrated 104 and 7 polymorphic sites of sbp-2 and rap-1a nucleic acid sequences, respectively, while those of sbp-2 and rap-1a amino acid sequences showed 46 and 4 high entropy peaks, respectively. Motifs analysis exhibited the distribution and conservation among sbp-2 and rap-1a sequences. The continuous and discontinuous B-cell epitopes have also been evaluated in this work. Therefore, our findings may be used to ameliorate the understanding inputs of molecular phylogeny, genetic diversity and antigenicity of B. bovis and B. bigemina Thailand stains.

Molecular Reports of Ruminant Babesia in Southeast Asia

The protozoon Babesia is a blood parasite transmitted by hard ticks and commonly parasitizes ruminants such as cattle, buffaloes, goats, and sheep. Babesiosis, the disease caused by Babesia infection, has been considered a potential threat to ruminant production due to the grave and enormous impact it brings. About 125 million ruminants are at risk of babesiosis in Southeast Asia (SEA), a region composed of 11 countries. In recent decades, molecular-based diagnostic platforms, such as polymerase chain reaction (PCR) assays, have been a reliable and broadly employed tool in Babesia detection. In this article, the authors compiled and summarized the molecular studies conducted on ruminant babesiosis and mapped the species, including B. bovis, B. bigemina, B. ovata, Babesia sp. Mymensingh, Babesia sp. Hue, and B. ovis, and determined the host diversity of ruminant Babesia in SEA.

Gastrointestinal nematodes from buffalo in Minoufiya Governorate, Egypt with special reference to Bunostomum phlebotomum

Gastrointestinal nematodes cause massive economic losses as an important impediment to the development of animals around the world. This study aimed to investigate the microscopical diagnosis of nematode parasites of buffalo from Minoufiya, Egypt and molecular characterization of Bunostomum phlebotomum. We examined 390 fecal samples with floatation and fecal culture techniques to recognize different genera of nematodes. The results revealed B. phlebotomum (2.56%), Strongyloides papillosus (3.85%), Toxocara vitulorum (7.69%), Haemonchus sp. (1.28%), and Dictyocaulus viviparus (1.28%). The recovered eggs and larvae of nematodes were identified as well as the adults of B. phlebotomum. Age-wise, sex-wise, and seasonal prevalences of the recovered nematodes were recorded. Sequence analysis of the ITS-2 gene of B. phlebotomum was highly identical (99-100%) to sequences from Australia and China and occurred in the same clade with B. trigoncephalum. In conclusion, the study presented the coprological survey of gastrointestinal nematodes, and the genetic characterization of B. phlebotomum from Minoufiya Governorate, Egypt for the first time.

A Survey of Tick Infestation and Tick-Borne Piroplasm Infection of Cattle in Oudalan and Séno Provinces, Northern Burkina Faso

In this study, cattle farms located in Oudalan and Séno, two provinces in the Sahel region, northern Burkina Faso, were surveyed. Cattle owners were interviewed, cattle were examined for tick infestation, and ticks as well as blood samples were collected during the dry season (October). Blood DNA samples were tested for Babesia and Theileria infections using nested PCRs and sequencing. A total of 22 herds, 174 Zebu cattle were investigated at 6 different sites. Overall, 76 cattle (43.7 %) from 18 farms (81.8%) were found infested with ticks. Cattle in Séno, adult cattle (>5 years) and those owned by the Fulani ethnic group were significantly (p < 0.05) more likely to be tick-infested. A total of 144 adult ticks belonging to five species namely: Hyalomma impeltatum, Hyalomma impressum, Hyalomma rufipes, Rhipicephalus evertsi evertsi, and Rhipicephalus guilhoni were collected from the animals. Piroplasms were detected in the blood DNA of 23 (13.2%) cattle. The cattle in Séno and adult cattle were significantly more likely to be piroplasm-positive. Five pathogens diversely distributed were identified. Theileria mutans (12/174), Babesia bigemina (5/174), Theileria annulata (3/174), and Theileria velifera (3/174) were detected for the first time in northern Burkina Faso, whereas Babesia occultans (1/174) was found for the first time in cattle in West Africa. The analysis of the sequences, including B. bigemina RAP-1a, T. annulata Tams1 genes, and the 18S rRNA genes of all the five protozoa, revealed identities ranging from 98.4 to 100% with previously published sequences. Phylogenetic analysis based on the 18S rRNA gene sequences located north Burkina Faso piroplasms in the same clade as isolates from Africa and other regions of the world. Notably, T. mutans sequences were distributed in two clades: the T. mutans Intona strain clade and the Theileria sp. (strain MSD)/ Theileria sp. B15a clade, suggesting the presence of at least two strains in the area. These findings indicate that the control of ticks and tick-borne diseases should be taken into account in strategies to improve animal health in the Sahel region.

Genetic Diversity of Babesia bovis MSA-1, MSA-2b and MSA-2c in China

The apicomplexan parasite Babesia bovis is a tick-borne intracellular hemoprotozoan parasite that is widespread across China. Genetic diversity is an important strategy used by parasites to escape the immune responses of their hosts. In our present study, 575 blood samples, collected from cattle in 10 provinces, were initially screened using a nested PCR (polymerase chain reaction) for detection of B. bovis infection. To perform genetic diversity analyses, positive samples were further amplified to obtain sequences of three B. bovis merozoite surface antigen genes (MSA-1, MSA-2b, MSA-2c). The results of the nested PCR approach showed that an average of 8.9% (51/575) of cattle were positive for B. bovis infection. Phylogenetic analyses of the predicted amino acid sequences revealed that unique antigen variants were formed only by Chinese isolates. Our findings provide vital information for understanding the genetic diversity of B. bovis in China.

Molecular survey of tick-borne pathogens infecting backyard cattle and water buffaloes in Quezon province, Philippines

Tick-borne diseases (TBD) cause enormous losses for farmers. Backyard raising comprises majority of the livestock population in the Philippines, but TBD information in backyard livestock is scarce. In this study, 48 cattle and 114 water buffalo samples from Quezon province, Philippines were molecularly screened for tick-borne pathogens. Anaplasma marginale (16.67%) and hemoplasma (20.99%) were detected in the samples. A. marginale infection (P=0.0001) was significantly higher in cattle, while hemoplasma infection (P=0.011) was significantly higher in water buffaloes. A. marginale isolates from this study were highly similar to previous isolates from the Philippines while Mycoplasma wenyonii and Candidatus Mycoplasma haemobos were the identified hemoplasma species. Our findings reveal additional information on the TBD situation of Philippine backyard livestock.

High resolution melting analysis of the 18S rRNA gene for the rapid diagnosis of bovine babesiosis

Background

Bovine babesiosis is caused by protozoan parasites of the genus Babesia and presents a wide spectrum of clinical manifestations. Disease severity depends on the type of Babesia species infection. Generally, B. bovis and B. bigemina are considered as the causative agents of bovine babesiosis; in addition, Babesia ovata and B. major are a group of benign bovine piroplasms. Therefore, species identification is important for diagnosis, epidemiological investigations and follow-up management.

Methods

Real-time PCR combined with high resolution melting (RT-PCR-HRM) analysis was used to detect and discriminate four Babesia species infective to cattle, including Babesia bovis, B. bigemina, B. major and B. ovata. The melting profiles and melting temperatures (Tm) of the amplicon targeting 18S rRNA revealed differences that can discriminate the four Babesia spp. Sensitivity and specificity of the analytical method were evaluated using 50 blood samples collected from experimentally infected cattle and 240 blood samples from areas where bovine babesiosis is an issue.

Results

RT-PCR-HRM analysis allowed to detect and discriminate four Babesia spp. (B. bovis, B. bigemina, B. major and B. ovata), which were responsible for bovine babesiosis in China. The protocol was validated with DNA samples from experimentally infected cattle and field infection in cattle.

Conclusions

Our results indicate that RT-PCR-HRM is a fast and robust tool for the simultaneous detection and discrimination of four Babesia species that are responsible for bovine babesiosis in China. This approach is applicable for both field and experimental samples, thus it could be useful in epidemiological investigations and diagnoses of bovine babesiosis.

Diagnostic Tools for the Identification of Babesia sp. in Persistently Infected Cattle

Bovine babesiosis is a tick-borne disease of cattle caused by the protozoan parasites of the genus Babesia. Babesia bovis, Babesia bigemina and Babesia divergens are considered by International health authorities (OIE) as the principal species of Babesia that cause bovine babesiosis. Animals that recover from a babesial primo infection may remain as persistent carriers with no clinical signs of disease and can be the source of infection for ticks that are able to acquire Babesia parasites from infected cattle and to transmit Babesia parasites to susceptible cattle. Several procedures that have been developed for parasite detection and diagnosis of this infectious carrier state constitute the basis for this review: A brief description of the direct microscopic detection of Babesia-infected erytrocytes; PCR-based diagnostic assays, which are very sensitive particularly in detecting Babesia in carrier cattle; in-vitro culture methods, used to demonstrate presence of carrier infections of Babesia sp.; animal inoculation, particularly for B. divergens isolation are discussed. Alternatively, persistently infected animals can be tested for specific antibabesial antibodies by using indirect serological assays. Serological procedures are not necessarily consistent in identifying persistently infected animals and have the disadvantage of presenting with cross reactions between antibodies to Babesia sp.

Genetic diversity of Babesia bovis in beef cattle in a large wetland in Brazil

Babesia bovis is the etiological agent of bovine babesiosis, a disease transmitted by Rhipicephalus microplus, which affects cattle herds in tropical and subtropical regions of the world, causing significant economic losses due to decreasing meat and milk yield. This study used molecular techniques to determine the occurrence and genetic diversity of B. bovis, based on the genes encoding the spherical body protein (sbp-2) and the merozoite surface antigens (MSAs) genes, in a herd of 400 Nellore (Bos indicus) sampled from beef cattle farms in the Pantanal region, state of Mato Grosso do Sul, Midwestern Brazil. The results of the nested PCR assays based on the sbp-2 gene indicated that 18 (4.5%) calves were positive for B. bovis; out of them, while 77.7% (14/18) were positive for the B. bovis msa-2b fragment, 66.6% (12/18) were positive for the msa-2c fragment. The phylogenetic analysis based on the maximum likelihood method using 14 sequences from msa-2b clones and 13 sequences from msa-2c clones indicated that the sequences detected in this study are clearly distributed in different cladograms. These findings corroborated the diversity analysis of the same sequences, which revealed the presence of 14 and 11 haplotypes of the msa-2b and msa-2c genes, respectively. Furthermore, the entropy analyses of amino acid sequences revealed 78 and 44 high entropy peaks with values ranging from 0.25 to 1.53 and from 0.27 to 1.09 for MSA-2B and MSA-2C, respectively. Therefore, the results indicate a low molecular occurrence of B. bovis in beef cattle sampled in the Brazilian Pantanal. Despite this, a high degree of genetic diversity was found in the analyzed B. bovis population, with possibly different haplotypes coexisting in the same animal and/or in the same studied herd.

First molecular detection and characterization of tick-borne pathogens in water buffaloes in Bohol, Philippines

The water buffalo industry is a vital part of the Philippine livestock economy and is an essential contributor to the developing local dairy industry. Although relatively less susceptible to diseases, water buffaloes can still be infected and can act as reservoirs of tick-borne pathogens (TBPs). However, limited information is available regarding the prevalence of tick-borne infections in water buffaloes in the Philippines. This study was conducted to identify TBPs harbored by water buffaloes and to characterize these pathogens molecularly. One hundred water buffalo blood samples collected from three areas in Bohol, Visayas region, Philippines were screened for various TBPs using pathogen-specific PCR assays. TBPs were detected in 46% of the samples (39% singly infected, 7% coinfected). The pathogens detected were Anaplasma marginale (29%), Babesia bovis (21%), and B. bigemina (3%). None of the blood samples were positive for Theileria annulata, T. orientalis, and B. ovata. A. marginale infection rates were significantly higher (37.5%) among water buffaloes aged ≤6 years (P = 0.046) than those >6 years old (18.2%) and was detected only in Bulgarian Murrah (36.1%) and US Murrah (25.9%) breeds. Phylogenetic analyses revealed that groEL sequences of A. marginale were 100% identical with isolates from the Philippines (Batangas and Cebu) and China. Two B. bigemina RAP-1a gene sequences were identical to each other and were homologous with previous isolates from Thailand, Indonesia, Uruguay, and the Philippines. Moreover, four B. bovis SBP-2 partial sequences obtained in this study had 92.4-99.7% identities. This study is the first molecular detection and characterization of A. marginale, B. bigemina and B. bovis in water buffaloes in the Visayas region, and the first molecular confirmation of B. bovis infection in water buffaloes in the country. The findings presented in this study may serve as baseline data for crafting effective tick-borne disease surveillance and prevention programs in Bohol and in the Philippines.

Molecular detection and genetic diversity of bovine Babesia spp., Theileria orientalis, and Anaplasma marginale in beef cattle in Thailand

Babesia spp., Theileria orientalis, and Anaplasma marginale are significant tick-borne pathogens that affect the health and productivity of cattle in tropical and subtropical areas. In this study, we used PCR to detect the presence of Babesia bovis, Babesia bigemina, and T. orientalis in 279 beef cattle from Western Thailand and A. marginale in 608 beef cattle from the north, northeastern, and western regions. The PCRs were performed using species-specific primers based on the B. bovis spherical body protein 2 (BboSBP2), B. bigemina rhoptry-associated protein 1a (BbiRAP-1a), T. orientalis major piroplasm surface protein (ToMPSP), and A. marginale major surface protein 4 (AmMSP4) genes. To determine the genetic diversity of the above parasites, amplicons of B. bovis and B. bigemina ITS1-5.8s rRNA gene-ITS2 regions (B. bovis ITS, B. bigemina ITS), ToMPSP, and AmMSP4 genes were sequenced for phylogenetic analysis. PCR results revealed that the prevalence of B. bovis, B. bigemina, T. orientalis, and A. marginale in the Western region was 11.1, 12.5, 7.8, and 39.1 %, respectively. Coinfections of two or three parasites were observed in 17.9 % of the animals sampled. The study revealed that the prevalence of A. marginale in the western region was higher than in the north and northeastern regions (7 %). Sequence analysis showed the BboSBP2 gene to be more conserved than B. bovis ITS in the different isolates and, similarly, the BbiRAP-1a was more conserved than B. bigemina ITS. In the phylogenetic analysis, T. orientalis MPSP sequences were classified into types 3, 5, and 7 as previously reported. A. marginale MSP4 gene sequences shared high identity and similarity with each other and clustered with isolates from other countries. This study provides information on the prevalence and genetic diversity of tick-borne pathogens in beef cattle and highlights the need for effective strategies to control these pathogens in Thailand.

Babesia ovata: Taxonomy, phylogeny and epidemiology

Babesia ovata, which is transmitted by Haemaphysalis longicornis, is an intraerythrocytic protozoan parasite of cattle. Based on its morphology, B. ovata is classified as a large-type Babesia. The developmental stages of B. ovata have been described both in cattle and the tick vector. In infected adult female ticks, the parasite is transovarially transmitted to the tick eggs. The sexual reproduction of B. ovata has been demonstrated in the tick midgut. The diagnostic tools that are currently available for the specific detection of B. ovata in cattle include microscopy and polymerase chain reaction assays. The development of improved molecular and serological diagnostic tools has been constrained by the limited availability of genetic data. B. ovata has been reported in cattle populations in Japan, Korea, China, Mongolia and Thailand. B. ovata was thought to be a benign parasite; however, infections in immuno compromised or Theileria orientalis-infected animals are clinically significant. Thus, control strategies aimed at minimizing the prevalence of B. ovata are vital. The taxonomy of B. ovata is unclear, and the phylogenetic position has not been well defined. Consequently, non-B. ovata species have sometimes been classified as B. ovata. In this review, we provide an outline of the lifecycle, geographical distribution, and control of B. ovata, and critically discuss the taxonomy and phylogeny of this bovine Babesia.

Comparison between conventional and molecular methods for diagnosis of bovine babesiosis (Babesia bovis infection) in tick infested cattle in upper Egypt

Ticks and tick-borne diseases are the main problems affecting the livestock production in Egypt. Bovine babesiosis has adverse effects on the animal health and production. A comparison of Giemsa stained blood smears, polymerase chain reaction (PCR) and nested PCR (nPCR) assays for detection of Babesia bovis infection in Egyptian Baladi cattle (Bos taurus) in reference to reverse line blot was carried out. The sensitivity of PCR and nested PCR (nPCR) assays were 65 and 100 % respectively. Giemsa stained blood smears showed the lowest sensitivity (30 %). According to these results using of PCR and nPCR target for B. bovis, [BBOV-IV005650 (BV5650)] gene are suitable for diagnosis of B. bovis infection. The 18Ss rRNA partial sequence confirmed that all the positive samples were Babesia bovis and all of them were deposited in the GenBank databases (Accession No: KM455548, KM455549 and KM455550).

Genetic diversity and antigenicity variation of Babesia bovis merozoite surface antigen-1 (MSA-1) in Thailand

Babesia bovis, an intraerythrocytic protozoan parasite, causes severe clinical disease in cattle worldwide. The genetic diversity of parasite antigens often results in different immune profiles in infected animals, hindering efforts to develop immune control methodologies against the B. bovis infection. In this study, we analyzed the genetic diversity of the merozoite surface antigen-1 (msa-1) gene using 162 B. bovis-positive blood DNA samples sourced from cattle populations reared in different geographical regions of Thailand. The identity scores shared among 93 msa-1 gene sequences isolated by PCR amplification were 43.5-100%, and the similarity values among the translated amino acid sequences were 42.8-100%. Of 23 total clades detected in our phylogenetic analysis, Thai msa-1 gene sequences occurred in 18 clades; seven among them were composed of sequences exclusively from Thailand. To investigate differential antigenicity of isolated MSA-1 proteins, we expressed and purified eight recombinant MSA-1 (rMSA-1) proteins, including an rMSA-1 from B. bovis Texas (T2Bo) strain and seven rMSA-1 proteins based on the Thai msa-1 sequences. When these antigens were analyzed in a western blot assay, anti-T2Bo cattle serum strongly reacted with the rMSA-1 from T2Bo, as well as with three other rMSA-1 proteins that shared 54.9-68.4% sequence similarity with T2Bo MSA-1. In contrast, no or weak reactivity was observed for the remaining rMSA-1 proteins, which shared low sequence similarity (35.0-39.7%) with T2Bo MSA-1. While demonstrating the high genetic diversity of the B. bovis msa-1 gene in Thailand, the present findings suggest that the genetic diversity results in antigenicity variations among the MSA-1 antigens of B. bovis in Thailand.

Molecular epidemiology of bovine Babesia spp. and Theileria orientalis parasites in beef cattle from northern and northeastern Thailand

Beef cattle production represents the largest cattle population in Thailand. Their productivity is constrained by tick-borne diseases such as babesiosis and theileriosis. In this study, we determined the prevalence of Babesia bigemina, Babesia bovis and Theileria orientalis using polymerase chain reaction (PCR). The genetic markers that were used for detection of the above parasites were sequenced to determine identities and similarity for Babesia spp. and genetic diversity of T. orientalis. Furthermore the risk factors for the occurrence of the above protozoan parasites in beef cattle from northern and northeastern parts of Thailand were assessed. A total of 329 blood samples were collected from beef cattle in 6 provinces. The study revealed that T. orientalis was the most prevalent (30.1%) parasite in beef cattle followed by B. bigemina (13.1%) and B. bovis (5.5%). Overall, 78.7% of the cattle screened were infected with at least one of the above parasites. Co-infection with Babesia spp. and T. orientalis was 30.1%. B. bigemina and T. orientalis were the most prevalent (15.1%) co-infection although triple infection with the three parasites was observed in 3.0% of the samples. Sequencing analysis revealed that B. bigemina RAP1 gene and B. bovis SBP2 gene were conserved among the parasites from different cattle samples. Phylogenetic analysis showed that the T. orientalis MPSP gene from parasites isolated from cattle in north and northeast Thailand was classified into types 5 and 7 as reported previously. Lack of tick control program was the universal risk factor of the occurrence of Babesia spp. and T. orientalis infection in beef cattle in northern and northeastern Thailand. We therefore recommend training of farmers on appropriate tick control strategies and further research on potential vectors for T. orientalis and elucidate the effect of co-infection with Babesia spp. on the pathogenicity of T. orientalis infection on beef in northern and northeastern Thailand.

Comparative transcriptome analysis of geographically distinct virulent and attenuated Babesia bovis strains reveals similar gene expression changes through attenuation

Background

Loss of virulence is a phenotypic adaptation commonly seen in prokaryotic and eukaryotic pathogens. This mechanism is not well studied, especially in organisms with multiple host and life cycle stages such as Babesia, a tick-transmitted hemoparasite of humans and animals. B. bovis, which infects cattle, has naturally occurring virulent strains that can be reliably attenuated in vivo. Previous studies suggest the virulence loss mechanism may involve post-genomic modification. We investigated the transcriptome profiles of two geographically distinct B. bovis virulent and attenuated strain pairs to better understand virulence loss and to gain insight into pathogen adaptation strategies.

Results

Expression microarray and RNA-sequencing approaches were employed to compare transcriptome profiles of two B. bovis strain pairs, with each pair consisting of a virulent parental and its attenuated derivative strain. Differentially regulated transcripts were identified within each strain pair. These included genes encoding for VESA1, SmORFs, undefined membrane and hypothetical proteins. The majority of individual specific gene transcripts differentially regulated within a strain were not shared between the two strains. There was a disproportionately greater number of ves genes upregulated in the virulent parental strains. When compared with their attenuated derivatives, divergently oriented ves genes were included among the upregulated ves genes in the virulent strains, while none of the upregulated ves genes in the attenuated derivatives were oriented head to head. One gene family whose specific members were consistently and significantly upregulated in expression in both attenuated strains was spherical body protein (SBP) 2 encoding gene where SBP2 truncated copies 7, 9 and 11 transcripts were all upregulated.

Conclusions

We conclude that ves heterodimer pair upregulation and overall higher frequency of ves gene expressions in the virulent strains is consistent with the involvement of this gene family in virulence. This is logical given the role of VESA1 proteins in cytoadherence of infected cells to endothelial cells. However, upregulation of some ves genes in the attenuated derivatives suggests that the consequence of upregulation is gene-specific. Furthermore, upregulation of the spherical body protein 2 gene family may play a role in the attenuated phenotype. Exactly how these two gene families may contribute to the loss or gain of virulence is discussed.

The molecular prevalence and MSA-2b gene-based genetic diversity of Babesia bovis in dairy cattle in Thailand

Bovine babesiosis is an economically significant disease that affects dairy farming operations in Thailand. In the present study, 1824 blood-DNA samples prepared from cattle bred in 4 different regions of the country (North, Northeast, Central, and South) were screened using a nested PCR for the specific detection of Babesia bovis. While the overall prevalence of B. bovis was 8.8%, the Central region of Thailand was found to be a high-risk area of the country, as the prevalence of the parasite was 15.0%. The positive rate was relatively higher among the animals of 1-5 years of age. The genetic diversity among the B. bovis parasites was also studied based on their MSA-2b gene, and the findings showed that the Thai sequences were dispersed across 8 of 13 total clades observed in the phylogram. Three of these clades were formed only of Thai sequences. Similarity among the deduced MSA-2b amino acid sequences determined in the present study was 68.3-100%. In conclusion, the present study found that all the locations surveyed were infected with B. bovis and that the parasite populations in Thailand were genetically diverse. Our findings highlight the need for further studies in Thailand to generate more information before a sound control strategy could be implemented against B. bovis.

The genetic diversity of merozoite surface antigen 1 (MSA-1) among Babesia bovis detected from cattle populations in Thailand, Brazil and Ghana

In the present study, we screened blood DNA samples obtained from cattle bred in Brazil (n=164) and Ghana (n=80) for Babesia bovis using a diagnostic PCR assay and found prevalences of 14.6% and 46.3%, respectively. Subsequently, the genetic diversity of B. bovis in Thailand, Brazil and Ghana was analyzed, based on the DNA sequence of merozoite surface antigen-1 (MSA-1). In Thailand, MSA-1 sequences were relatively conserved and found in a single clade of the phylogram, while Brazilian MSA-1 sequences showed high genetic diversity and were dispersed across three different clades. In contrast, the sequences from Ghanaian samples were detected in two different clades, one of which contained only a single Ghanaian sequence. The identities among the MSA-1 sequences from Thailand, Brazil and Ghana were 99.0–100%, 57.5–99.4% and 60.3–100%, respectively, while the similarities among the deduced MSA-1 amino acid sequences within the respective countries were 98.4–100%, 59.4–99.7% and 58.7–100%, respectively. These observations suggested that the genetic diversity of B. bovis based on MSA-1 sequences was higher in Brazil and Ghana than in Thailand. The current data highlight the importance of conducting extensive studies on the genetic diversity of B. bovis before designing immune control strategies in each surveyed country.

Epidemiological survey of Babesia bovis and Babesia bigemina infections of cattle in Philippines

A total of 250 blood samples were collected from clinically healthy cattle in five provinces of Philippines. DNA was extracted from the samples and analyzed by nested PCR assays for an epidemiological survey of Babesia bovis and Babesia bigemina infections. Out of the 250 samples, 27 (10.8%) and 16 (6.4%) were positive for B. bovis infection and B. bigemina infection, respectively. Mixed infections were detected in a total of 4 samples (1.6%). Our data provide baseline information regarding the epidemiology of B. bovis and B. bigemina infections in cattle in Philippines, which can be utilized in developing proper strategies for disease control and management.

Theileria, Babesia, and Anaplasma detected by PCR in ruminant herds at Bié Province, Angola

Distribution of Anaplasma spp., Babesia spp., Theileria spp., and Ehrlichia ruminantium, was for the first time studied in Bié Province, central Angola. We examined 76 blood samples of cattle originated from seven farms, and 13 blood samples of goats from two farms employing molecular genetic tools (PCR). Most prevalent was A. ovis-infection in goats (100%) and A. marginale-infection in cattle (38% of examined animals, and six out of seven farms). B. bigemina-infection was detected in only one specimen at Andulo, whereas B. bovis was not detected in Bié. We did not detected T. parva, the causative agent of serious diseases in cattle; nevertheless, infection by T. velifera was quite frequent (14% of examined animals, and five out of seven farms). Causative agent of heartwater disease - E. ruminantium, was not detected. Taking into account short-term perspective of PCR methods in monitoring of epidemiological status in herds, the number of infected animals and distribution of detected pathogens should not be ignored.

Molecular detection and identification of Babesia bovis and Babesia bigemina in cattle in northern Thailand

Although Babesia bovis and Babesia bigemina infections cause economic losses in the cattle industry in northern Thailand, there is inadequate information on Babesia isolates present in the area. Therefore, to determine the prevalence and genetic relationship between Babesia isolates, we screened 200 blood samples of cattle from Chiang Rai, Chiang Mai, and Lumpang provinces of northern Thailand. A nested polymerase chain reaction using primers targeting B. bovis spherical body protein 2 (BboSBP2) and B. bigemina rhoptry-associated protein 1a (BbiRAP-1a) genes revealed a prevalence of 12 and 21 % for B. bovis and B. bigemina, respectively, while that of mixed infections was 6.5 % samples. The prevalences of B. bovis in Chiang Rai, Chiang Mai, and Lumpang were 9.5, 3.7, and 25.5 %, respectively. For B. bigemina, the prevalences were 15.8, 12.9, and 39.2 % in Chiang Rai, Chiang Mai, and Lumpang, respectively. Mixed infections with B. bovis and B. bigemina were 6.3 % in Chiang Rai, 1.9 % in Chiang Mai, and 13.7 % in Lumpang. The identical sequences of either BboSBP2 gene or BbiRAP-1a gene were shared among the Babesia isolates in the three provinces of northern Thailand. Further analysis using the internal transcribed spacer gene revealed at least four genotypes for B. bovis and five genotypes for B. bigemina in northern Thailand, while the sequences present great genetic diversities in the different isolates. Overall, we have demonstrated a high prevalence and polymorphism of Babesia parasites in northern Thailand calling for the need to design effective control programs for bovine babesiosis.

Recent insights into alteration of red blood cells by Babesia bovis: moovin' forward

Over the past decade or so, our understanding of the biology of apicomplexan parasites has increased dramatically, particularly in the case of malaria. Notable achievements are the availability of complete genome sequences, transcriptome and proteome profiles and the establishment of in vitro transfection techniques for asexual-stage malaria parasites. Interestingly, despite their major economic importance and striking similarities with malaria, Babesia parasites have been relatively ignored, but change is on the horizon. Here, we bring together recent work on Babesia bovis parasites which are beginning to unravel the molecular mechanisms that underlie the pathogenesis of babesiosis and highlight some opportunities and challenges that lie ahead.

Development and evaluation of two nested PCR assays for the detection of Babesia bovis from cattle blood

We developed and evaluated two nested polymerase chain reaction (nPCR) assays for the diagnosis of Babesia bovis infection in cattle based on two membrane protein genes from B. bovis, BBOV_IV005650 (BV5650) and BBO_IV008970 (BV8970). The specificities and sensitivities of the tests were compared with B. bovis Rhoptery associated protein 1 gene (RAP-1) nPCR. The specificity of the tests was 100% for B. bovis DNA. The sensitivities of nPCR to B. bovis from the in vitro cultured parasites were as low as 10(-8)%, 10(-6)%, and 10(-7)% parasitemia for BV5650, BV8970, and RAP-1 nPCR, respectively. The nPCR detected as little as 1 fg genomic DNA per test for BV5650 and 100fg per test for both BV8970 and RAP-1 genes. For field applications, the sensitivity was evaluated to a total of 165 field samples from Ghana, Mongolia, Brazil and Japan. The nPCR assay of BV5650 was the most sensitive for the detection of B. bovis from the field samples. The BV5650 nPCR assay provides a good diagnostic tool for laboratory diagnostic assessment of B. bovis infection in cattle worldwide.