Epidemiological studies on tick-borne diseases of cattle in Central Equatoria State, Southern Sudan

Prevalence and Risk Factors Associated with Theileria annulata Infection in Two Bovine Portuguese Autochthonous Breeds

Tropical Bovine Theileriosis is an important tick-borne disease. This study aims to assess the occurrence of Theileria annulata infection in two indigenous Portuguese cattle breeds. A total of 843 blood samples collected from animals of Alentejana (n = 420) and Mertolenga (n = 423) breeds were analyzed. The detection of Theileria annulata was determined by amplification of a fragment of the merozoite-pyroplasm surface antigen gene with 319 base pairs (bp). The prevalence found (10.8%) is lower than that reported in previous studies (21.3%). A statistically significant difference was found for positivity between breeds (p < 0.05). There is also a higher probability of older animals being positive compared to younger ones (p < 0.05). The region where Mertolenga animals are located is shown to have a significant impact on positivity (p < 0.05). Thus, the development of sustainable T. annulata control strategies and their implementation, adapted to the epidemiological conditions of higher risk, will be extremely important.

Genetic Resistance of Bovines to Theileriosis

Diseases caused by ticks have a high impact on the health, welfare, and productivity of livestock species. They are also an important cause of economic losses in farms worldwide. An example of such diseases is theileriosis, which can be controlled by drugs or vaccines, although these are not fully efficient. Therefore, there is a need to develop alternative and more sustainable and efficient complementary strategies. These may involve the identification and selection of animals more resistant to the disease. Several previous studies have identified significant differences in resistance between different breeds, with resistant breeds typically identified as those native to the region where they are being studied, and susceptible as those from exotic breeds. These studies have indicated that resistance traits are intrinsically related to the modulation of the immune response to infection. This review aims to systematize the general knowledge about theileriosis, emphasize resistance to this disease as a sustainable control strategy, and identify which traits of resistance to the disease are already known in cattle.

In vitro growth inhibitory effect of selected 18β-glycyrrhetinic acid esters on Theileriaannulata

Glycyrrhetinic acid (GA) is one of the important Pentacyclic Triterpenoids (PT) found in the roots of licorice. This study aimed to evaluate the in vitro growth inhibitory effect of 18β-GA (18β-Glycyrrhetinic acid) and C-30 esters against Theileria annulata, the causative agent of Tropical Bovine Theileriosis. C-30 esters of 18β-GA were synthesized and their structures were elucidated using spectroscopy. The pharmacodynamic properties of 18β-GA and its C-30 esters were predicted using DataWarrior and Swiss ADME tools. Cattle isolates of T. annulata schizont-infected bovine lymphoblastoid cells were cultured using standard conditions and the growth inhibitory effect of GA and its esters were evaluated using MTT assay. The isopropyl ester of 18β-GA (GI₅₀- 1.638 μM; R²- 0.818) showed improved anti-theileriosis efficacy than other 18β-GA derivatives. The propyl (GI₅₀ - 5.549 μM), ethyl (GI₅₀ - 5.638 μM), and benzyl (GI₅₀ - 7.431 μM) esters also showed considerable inhibitory effect. The GI₅₀ value for 18β-GA was recorded as 6.829 μM. This study throws light on the usefulness of 18β-GA and its esters for the treatment of Tropical Bovine Theileriosis.

Molecular detection of selected tick-borne pathogens infecting cattle at the wildlife-livestock interface of Queen Elizabeth National Park in Kasese District, Uganda

In Uganda, ticks and tick-borne diseases (TBDs) pose a big challenge to farmers. They reduce cattle productivity and cause severe economic damage. Several studies have documented the prevalence of tick-borne pathogens in cattle; however, their genetic characteristics and the role of wildlife-livestock interaction in the epidemiology of the TBDs are not well documented. This study assessed the prevalence and genetic diversity of various tick-borne pathogens (TBPs) as well as the risk factors associated with the occurrence of TBPs in blood samples of 208 randomly selected cattle from 16 farms located around Queen Elizabeth National Park (QENP) in Kasese District in western Uganda. Farming practices, disease challenges, and the level of wildlife-livestock interactions were assessed by a questionnaire survey amongst farm owners. Polymerase chain reaction (PCR) assays revealed that 62.9% (131/208) cattle samples were positive for one or more pathogens. Using specific PCR assays, we detected Theileria spp., Theileria parva, Anaplasma marginale, Anaplasma platys-like, and Babesia bigemina at 50.5%, 27.9%, 19.2%, 11.5% and 8.7%, respectively. We also confirmed the infection of samples by Theileria velifera and Theileria mutans after sequencing the Theileria spp. 18S rRNA gene. The risk factors associated with the occurrence of TBPs included communal grazing, herd size, age, and proximity to QENP. Phylogenetic analysis of the T. parva p104 gene showed a high identity to the previous isolates from Uganda and other East African countries and clustered closer to the buffalo (Syncerus caffer) isolates, suggesting a possible cross-species transmission. The sequences of A. marginale groEL and B. bigemina RAP-1a formed well-supported clades with high identities to the previous isolates identified from central and eastern Uganda. The isolates obtained from A. phagocytophilum 16S rRNA gene sequences showed relationship with A. platys-like, Anaplasma sp., uncultured Anaplasma species and A. phagocytophilum isolates from Africa, Asia, Europe, and the USA. The findings of the present study showed that TBDs are still a burden to farmers and that management practices in this area may increase the transmission of pathogens between livestock and wildlife.

Prevalence of serum antibodies of tick-borne diseases and the presence of Rhipicephalus microplus in communal grazing cattle in the north-eastern region of the Eastern Cape Province of South Africa

A survey to determine the prevalence of tick-borne diseases (TBDs) and ticks infesting cattle was conducted in the communal areas of the north-eastern region of the Eastern Cape Province (ECP) between January 2019 and October 2019. Tick counts, packed cell volume (PCV), body condition scores (BCS), and serological test for TBDs were seasonally conducted in communally grazed cattle (n = 240) in Joe Gqabi district in two local municipalities (Elundini and Senqu). A standard indirect fluorescent antibody test (IFAT) was used to determine antibodies to Babesia bigemina, Babesia bovis, and Ehrlichia ruminantium and indirect enzyme-linked immunosorbent assay (ELISA) was employed for antibodies to Anaplasma marginale detection. The highest tick loads were observed on cattle during the hot-wet and post-rainy seasons and lowest during the cool-dry season. The E. ruminantium prevalence in Elundini was 16% and 14% in post-rainy and hot-dry seasons respectively and 15% at Senqu during the post-rainy season. B. bigemina prevalence was highest at Elundini (18%) and Senqu (16%) during the post-rainy season and hot-wet season respectively. Cattle BCS was negatively correlated with E. ruminantium (P < 0.01; r = - 0.203), B. bovis (P < 0.01; r = - 0.125), and A. marginale (P < 0.01; r = - 0.122) seroprevalence. The PCV was negatively correlated with B. bigemina (P < 0.01; r = - 0.138) seroprevalence. On the other hand, E. ruminantium was positively correlated with Amblyomma hebraeum (P < 0.05; r = 0.112) infestation, while B. bovis (P < 0.05; r = 0.134) and B. bigemina (P < 0.05; r = 0.188) were positively correlated with Rhipicephalus microplus infestation, and B. bigemina (P < 0.05; r = 0.077) was positively correlated with Rhipicephalus decoloratus infestation. Our study reports for the first time the presence of R. microplus in the study area. Further research is, however, needed to better understand seroprevalence and the transmission mode of TBDs to cattle so that effective disease control measures can be developed.

Tick Fauna and Associated Rickettsia, Theileria, and Babesia spp. in Domestic Animals in Sudan (North Kordofan and Kassala States)

Ticks and tick-borne diseases (TBDs) have a major economic impact on animal production worldwide. In the present study, 2410 ticks were collected from January to August 2017 from livestock and other domestic animals in North Kordofan and Kassala, Sudan, for species identification and investigation of Rickettsia spp. and piroplasms, either individually or as pools containing up to 10 ticks by molecular methods. In total, 13 tick species were identified by morphology and 16S rDNA sequencing. The most frequent tick species were Hyalomma impeltatum (24.90%), Rhipicephalus evertsi evertsi (18.84%), Amblyomma lepidum (16.06%), and Rhipicephalus camicasi (12.49%). A pan-Rickettsia real-time PCR revealed an overall minimum infection rate (MIR) with Rickettsia spp. of 5.64% (136 positive tick pools/2410 total ticks). Rickettsia africae and Rickettsia aeschlimannii were the most frequently identified species by sequencing. Furthermore, the following highly pathogenic livestock parasites were detected: Theileria annulata, Theileria lestoquardi, Theileria equi, and Babesia caballi. The present study documented Rhipicephalus afranicus as well as Rickettsia conorii israelensis, Rickettsia massiliae, and Babesia pecorum for the first time in Sudan. These findings are significant for the animal production sector as well as in terms of One Health, as the detected Rickettsia spp. can cause serious illness in humans.

Molecular Detection, Phylogenetic Analysis, and Genetic Diversity of Theileria annulata, Babesia bigemina, and Anaplasma marginale in Cattle in Three Districts of Egypt

BACKGROUND

Under the poor hygienic conditions, tick-borne pathogens cause severe economic losses to the cattle industry.

PURPOSE

The current study investigated the presence of Theileria annulata, Babesia bigemina, and Anaplasma marginale, the most relevant tick-borne pathogens in cattle, in 3 provinces of Egypt utilizing species-specific PCR assays.

METHODS

PCR was conducted, on bovine blood specimens, using primers targeting the T. annulata merozoite-piroplasm surface antigen (Tams1, 768 bp), A. marginale major surface protein-1b gene (msp1b, 265 bp), and B. bigemina small subunit ribosomal RNA gene (SSrRNA, 543 bp).

RESULTS

PCR findings revealed overall prevalences of T. annulata, B. bigemina, and A. marginale as 22.0% (33/150), 19.33% (29/150), and 10.6% (16/150), respectively. The co-infection with two or three pathogens was detected in 20.0% (30/150) of examined specimens. Sequence analyses indicated that T. annulata and A. marginale varied from those of corresponding GenBank sequences revealing percent identities ranging from 90.68 to 97.75% and from 94.98 to 98.63%, respectively. On the other hand, the obtained B. bigemina sequences showed a high similarity with those previously reported in GenBank with a percent identity ranging from 98.85 to 100%.

CONCLUSION

T. annulata was the most prevalent tick-borne pathogen in examined bovine specimens. The genetic diversity of markers used for identification of T. annulata and A. marginale should be highly considered.

Current status of tropical theileriosis in Northern Africa: A review of recent epidemiological investigations and implications for control

Tropical theileriosis caused by the apicomplexan hemoparasite Theileria annulata is a tick-borne disease that constraints livestock production in parts of Europe, Asia and Africa. Four Hyalomma tick species transmit T. annulata in at least eight Africa countries (Mauritania, Morocco, Algeria, Tunisia, Egypt, Sudan, South Sudan and Ethiopia). The two dominant T. annulata vector ticks present in Africa, H. scupense and H. anatolicum, underlie two different patterns of transmission, which in turn greatly influence the epidemiology of tropical theileriosis. H. dromedarii and H. lusitanicum are also capable of transmitting T. annulata in North Africa, but their roles are associated with specific production systems and agro-ecological contexts. The emergence of resistance to the most widely used theilericidal compound, buparvaquone, continues to limit the effectiveness of chemotherapy. In addition, acaricide use is increasingly becoming unsustainable. Deployable T. annulata attenuated live vaccines established from local strains in Tunisia, Sudan and Egypt are available, and recent work has indicated that these vaccines can be protective under conditions of natural transmission. However, vaccination programmes may vary over space and time due to differences in the prevalence of disease amongst cattle populations, as well seasonal variation in vector activity. We review recent descriptive and analytical surveys on the epidemiology of T. annulata infection with reference to (a) demographic aspects such as breeds and ages of cattle herds previously exposed to distinct T. annulata infection pressures and (b) seasonal dynamics of tick activity and disease transmission. We then discuss how the wider endemic patterns that we delineate can underpin the development and execution of future vaccination programmes. We also outline options for integrated control measures targeting tick vectors and husbandry practices.

The Rhipicephalus appendiculatus tick vector of Theileria parva is absent from cape buffalo (Syncerus caffer) populations and associated ecosystems in northern Uganda

Rhipicephalus appendiculatus is the major tick vector of Theileria parva, an apicomplexan protozoan parasite that causes the most economically important and lethal disease of cattle in East and central Africa. The African cape buffalo (Syncerus caffer) is the major wildlife host of T. parva from southern Uganda and Kenya to southern Africa. We show herein that R. appendiculatus appears to be absent from the two largest national parks in northern Uganda. Syncerus caffer is common in both of these national parks, specifically Murchison falls (MFNP) and Kidepo Valley (KVNP). We re-confirmed the previously reported absence of T. parva in buffalo sampled in the two northern parks based on RLB data using a nested PCR based on the T. parva p104 gene. By contrast, T. parva-infected R. appendiculatus ticks and parasite-infected buffalo were present in Lake Mburo (LMNP) in South central Uganda. This suggests that the distribution of R. appendiculatus, which is predicted to include the higher rainfall regions of northern Uganda, may be limited by additional, as yet unknown factors.

Diagnostic tools of caprine and ovine anaplasmosis: a direct comparative study

Background

The diagnosis of anaplasmosis is rather conflicting with other haemoprotozoans. Hence, the study aimed to compare and evaluate the efficiency of competitive ELISA (cELISA), indirect fluorescence antibody (IFA), and Polymerase chain reaction (PCR) for precise diagnosis of Anaplasma spp. and to assess their concordance with microscopic examination (ME).

Results

A total of 312 blood samples (189 sheep and 123 goats) were examined for Anaplasma infection during a 1 year period. Giemsa-stained blood smears were examined under the microscope. IFA and cELISA were used for the detection of Anaplasma spp. antibodies. PCR was used as a standard of truth and for the identification of Anaplasma species. Using cELISA assay, 47.4% (148) were positive (93 sheep and 55 goats) with a sensitivity and specificity of 91.9, and 86.9%, respectively. Using IFA, it was found that 57.4% (179)were positive (113 sheep and 66 goats) with a sensitivity and specificity of 100, and 93.3%, respectively. PCR assay identified A. ovis in 49 (25.3%) sheep and 30 (15.5%) goats, and A. phagocytophilumin 74 (38.1%) sheep and 41 (20.8%) goats.

Conclusions

High sensitivity and specificity values of IFA and ELISA tests compared to microscopic examination strongly support their utility in the diagnosis of Anaplasma infection. PCR was a more specific diagnostic tool that allows to discriminate between Anaplasma subspecies, which makes it the method of choice for anaplasmosis diagnosis.

Genes encoding two Theileria parva antigens recognized by CD8+ T-cells exhibit sequence diversity in South Sudanese cattle populations but the majority of alleles are similar to the Muguga component of the live vaccine cocktail

East Coast fever (ECF), caused by Theileria parva infection, is a frequently fatal disease of cattle in eastern, central and southern Africa, and an emerging disease in South Sudan. Immunization using the infection and treatment method (ITM) is increasingly being used for control in countries affected by ECF, but not yet in South Sudan. It has been reported that CD8⁺ T-cell lymphocytes specific for parasitized cells play a central role in the immunity induced by ITM and a number of T. parva antigens recognized by parasite-specific CD8⁺ T-cells have been identified. In this study we determined the sequence diversity among two of these antigens, Tp1 and Tp2, which are under evaluation as candidates for inclusion in a sub-unit vaccine. T. parva samples (n = 81) obtained from cattle in four geographical regions of South Sudan were studied for sequence polymorphism in partial sequences of the Tp1 and Tp2 genes. Eight positions (1.97%) in Tp1 and 78 positions (15.48%) in Tp2 were shown to be polymorphic, giving rise to four and 14 antigen variants in Tp1 and Tp2, respectively. The overall nucleotide diversity in the Tp1 and Tp2 genes was π = 1.65% and π = 4.76%, respectively. The parasites were sampled from regions approximately 300 km apart, but there was limited evidence for genetic differentiation between populations. Analyses of the sequences revealed limited numbers of amino acid polymorphisms both overall and in residues within the mapped CD8⁺ T-cell epitopes. Although novel epitopes were identified in the samples from South Sudan, a large number of the samples harboured several epitopes in both antigens that were similar to those in the T. parva Muguga reference stock, which is a key component in the widely used live vaccine cocktail.

Rapid diagnosis of Theileria annulata by recombinase polymerase amplification combined with a lateral flow strip (LF-RPA) in epidemic regions

Rapid and accurate diagnosis of Theileria annulata infection contributes to the formulation of strategies to eradicate this parasite. A simple and efficient diagnostic tool, recombinase polymerase amplification (RPA) combined with a lateral flow (LF) strip, was used in detection of Theileria and compared to other methods that require expensive instruments and skilled personnel. Herein, we established and optimized an LF-RPA method to detect the cytochrome b gene of T. annulata mitochondrial DNA from experimentally infected and field-collected blood samples. This method has many unparalleled characteristics, including that it is rapid (clear detection in 5min at constant temperature), sensitive (the limitation of detection is at least 2pg genomic DNA), and specific (no cross-reaction with other piroplasms that infect cattle). The LF-RPA assay was evaluated via testing 17 field blood samples and comparing the results of that of a PCR, showing 100% agreement, which demonstrates the ability of the LF-RPA assay to detect T. annulata infections in small number of samples (n=17). Taken together, the results indicate that this method could be used as an ideal diagnostic tool for detecting T. annulata in endemic regions with limited to fewer and local resources and could also be a potential technique for the surveillance and control of blood protozoa.

Evaluating an indirect rMPSP enzyme-linked immunosorbent assay for the detection of bovine Theileria infection in China

Bovine theileriosis, a tick-borne protozoan disease caused by Theileria annulata, Theileria orientalis and Theileria sinensis, is widespread in China and is a serious economic problem for the Chinese livestock industry. In this study, recombinant major piroplasma surface proteins (MPSP) of T. annulata, T. orientalis and T. sinensis based on MPSP genes were expressed in Escherichia coli BL21(DE3). The immunogenicity and specificity of the three purified recombinant MPSP proteins were evaluated with the reference positive sera of T. annulata, T. orientalis, T. sinensis, Babesia bovis, B abesia bigemina, Babesia major, Babesia motasi, Theileria luwenshuni, Theileria uilenbergi and Anaplasma ovis using an enzyme-linked immunosorbent assay (ELISA) or western blotting. The results showed that all three of the rMPSP proteins had a strong reaction with the sera from cattle infected with T. annulata, T. orientalis and T. sinensis via western blotting but not with other piroplasma and Anaplasma species. Then, the rMPSP protein of T. sinensis was used to develop an iELISA for detecting the three Theileria species infections. The specificity and sensitivity were 95.7 and 95.5 %, respectively, with a threshold of 28.8 % of the specific mean antibody rate (AbR). Finally, 2473 field-collected bovine sera, from 42 prefectures of 17 provinces in China, were tested using the ELISA to evaluate the prevalence of bovine theileriosis, and the average positive rate was 43.6 %. The developed iELISA could be a suitable tool to detect the three bovine Theileria species, and the data also provided important information regarding the current prevalence of bovine theileriosis in China.

Molecular characterization of Theileria orientalis from cattle in Ethiopia

This study reports the first molecular characterization of Theileria orientalis in local breeds of cattle in Ethiopia. A conventional PCR utilizing major piroplasm surface protein (MPSP) gene and an established multiplexed tandem PCR (MT-PCR) were used to characterize T. orientalis and to assess the infection intensity, respectively. Of 232 blood samples tested, T. orientalis DNA was detected in only 2.2% of samples using conventional PCR; two genotypes buffeli (1.3%; 3/232) and type 5 (0.9%; 2/232) of T. orientalis were detected. Phylogenetic analysis revealed that the buffeli MPSP sequences from Ethiopia were closely related to those reported from Kenya, Sri Lanka and Myanmar, and type 5 sequences from Ethiopia grouped with those from Korea, Japan, Vietnam and Thailand. A higher number of samples (3.9%; 9/232) were test-positive by MT-PCR and four genotypes (buffeli, chitose, ikeda and type 5) of T. orientalis were detected. The average intensity of infections with genotypes buffeli (DNA copy numbers 11,056) and type 5 (7508) were significantly higher (P<0.0001) than the pathogenic genotype ikeda (61 DNA copies). This first insight into T. orientalis from cattle in Ethiopia using MPSP gene provides a basis for future studies of T. orientalis in various agroclimatic zones and of the impact of oriental theilerosis on cattle in this and other countries of Africa.

Serological and molecular diagnostic surveys combined with examining hematological profiles suggests increased levels of infection and hematological response of cattle to babesiosis infections compared to native buffaloes in Egypt

BACKGROUND

Babesiosis threatens the development of the cattle and buffaloes industries in Egypt and improved control is needed. The main objectives of this study are surveying the presence of bovine babesiosis in distinct selected bovine and buffalo populations in Egypt using novel molecular and previously validated serological methods, while also comparing the occurrence of hematological alterations among Babesia infected cattle and buffalos.

METHODS

A total of 253 and 81 blood samples from apparently healthy cattle and buffaloes, respectively, were randomly collected from diverse locations in Egypt. All samples were tested for Babesia bovis and B. bigemina infection using blood film examination, competitive ELISA (cELISA) and PCR. Novel semi-nested and nested PCR assays for the detection of B. bovis and B. bigemina respectively, were developed and used to analyze DNA extracted from bovine and buffalo samples. Hematological profiles were studied using a hematological analyzer.

RESULTS

Blood films examination revealed 13.8% and 7.4% Babesia infection rates in cattle and buffaloes, respectively. However, in cattle, the cELISA detected 32.8%, 21.3% and 10.7% infection rates with B. bigemina, B. bovis and mixed infection, respectively. In addition, cELISA identified 22.2%, 22.2% and 6.2% infection rates with B. bigemina, B. bovis and mixed infection, respectively in buffaloes. The semi-nested PCR assay showed that 15% of the tested samples were positive for B. bovis in cattle, but just 3% in buffaloes. Infections with B. bigemina were also found in cattle (32.4%), but not in buffaloes upon nested PCR analysis. Sequencing analysis confirmed the identity of the PCR amplicons and showed that Egyptian genotypes of B. bigemina and B. bovis highly resemble sequences previously deposited in GenBank. Hemograms performed on the sampled animals revealed macrocytic hypochromic anemia associated with reduced platelet counts in infected cattle with babesiosis. In addition, marked increases in total leukocyte and granulocytic counts and decreases in lymphocytic counts were found in infected cattle. In contrast, no such hematological anomalies were found in presumably Babesia-infected buffaloes.

CONCLUSIONS

Frequent occurrence of babesiosis among apparently healthy bovines in Egypt, suggests the need for appropriately designed prevalence studies in this country. Infected bovine, but not buffalo, populations often present hematological disorders compatible with intravascular hemolysis and thrombocytopenia.

Correlation between Platelets and Red Blood Cells Parameters in Cattle Theileriosis

The purpose of the study is to investigate the values for platelets (PLT) count, plateletcrit (PCT), mean platelet volume (MPV), platelet distribution width (PDW) and the correlation with the parallel red blood cell parameters, packed cell volume (PCV), mean corpuscular volume (MCV), and red blood cell distribution width (RDW) in cattle Theileriosis. A total number of 25 cows were subjected to study. Out of them 18 cows were suffered from Theileriosis, the remained 7 cows were clinically healthy and kept as control. Red blood cells (RBCs) and platelet indices were measured in whole blood samples collected on EDTA. Animals infected with Theileria were classified into two groups based on total erythrocytes count. Group 1: included animals that had total RBCs count above 5 x 106/mm3. Group 2: included animals that had total RBCs count below 5 x 106/mm3. Comparing data from theileria infected groups with the control group revealed that there was a significant decrease in total RBCs count only in group 2 (p<0.01). MCV showed significant decreases in group 1 (p<0.01) and group 2 (p<0.05), PCV was significantly decreased in both groups (p<0.01), RDW was significantly increased only in group 2 (p<0.05), PLT count was significantly decreased only in group 2 (p<0.05), PCT was significantly decreased only in group 2 (p<0.05), no significant changes were observed in MPV and PDW. Comparing data from group 1 with group 2 revealed that RBCs count, PCV and PLT count were significantly higher in group 1 than group 2. Furthermore, MCV value was significantly higher in group 2 than group 1. RDW was significantly higher in group 2 than group 1. The present study revealed that in cattle Theileriosis, PLT indices greatly affected by the degree of anemia. Furthermore, the decrease in PLT count and PCT usually accompany oligocythemia.

Can Anaplasma ovis in small ruminants be neglected any longer?

Anaplasma species are obligate intracellular rickettsial pathogens transmitted by ticks with an impact on human and animal health. Anaplasma ovis infects sheep and goats in many regions of the world, and it can be diagnosed by different methods like Giemsa staining, PCR or competitive ELISA. In this study, a PCR based on the gene coding for major surface protein 4 (MSP-4) was used to examine field samples collected from sheep in different countries. Altogether, 1161 blood samples from Turkey (n = 830), Iraq (n = 195), Sudan (n = 96) and Portugal (n = 40) were examined, of which 31.4%, 66.6% 41.6% and 82.5%, respectively, were positive. This indicates high prevalence of A. ovis in the countries under investigation, and it can be assumed that the situation in other areas of the world might be similar. Thus, A. ovis should be considered as an important constraint of livestock production, and further efforts are needed to better understand the epidemiology and to implement suitable control measures.

To be or not to be associated: power study of four statistical modeling approaches to identify parasite associations in cross-sectional studies

A growing number of studies are reporting simultaneous infections by parasites in many different hosts. The detection of whether these parasites are significantly associated is important in medicine and epidemiology. Numerous approaches to detect associations are available, but only a few provide statistical tests. Furthermore, they generally test for an overall detection of association and do not identify which parasite is associated with which other one. Here, we developed a new approach, the association screening approach, to detect the overall and the detail of multi-parasite associations. We studied the power of this new approach and of three other known ones (i.e., the generalized chi-square, the network and the multinomial GLM approaches) to identify parasite associations either due to parasite interactions or to confounding factors. We applied these four approaches to detect associations within two populations of multi-infected hosts: (1) rodents infected with Bartonella sp., Babesia microti and Anaplasma phagocytophilum and (2) bovine population infected with Theileria sp. and Babesia sp. We found that the best power is obtained with the screening model and the generalized chi-square test. The differentiation between associations, which are due to confounding factors and parasite interactions was not possible. The screening approach significantly identified associations between Bartonella doshiae and B. microti, and between T. parva, T. mutans, and T. velifera. Thus, the screening approach was relevant to test the overall presence of parasite associations and identify the parasite combinations that are significantly over- or under-represented. Unraveling whether the associations are due to real biological interactions or confounding factors should be further investigated. Nevertheless, in the age of genomics and the advent of new technologies, it is a considerable asset to speed up researches focusing on the mechanisms driving interactions between parasites.

Theileria infection in domestic ruminants in northern Ethiopia

Piroplasmosis caused by different tick-borne hemoprotozoan parasites of the genera Theileria and Babesia is among the most economically important infections of domestic ruminants in sub-Saharan Africa. A survey for piroplasm infection was conducted in three locations in Northern Ethiopia. Of 525 domestic ruminants surveyed, 80% of the cattle, 94% of the sheep and 2% of the goats were positive for different Theileria spp. based on PCR of blood followed by DNA sequencing. Sheep had a significantly higher rate of infection compared with cattle (P<0.0003) and both sheep and cattle had higher rates of infection compared to goats (P<0.0001). Four species of Theileria were detected in cattle: T. velifera, T. mutans, T. orientalis complex and T. annulata with infection rates of 66, 8, 4, and 2%, respectively. This is the first report of T. annulata, the cause of Tropical Theileriosis in Ethiopia. Of the two Theileria spp. detected in small ruminants, T. ovis was highly prevalent (92%) in sheep and rare in goats (1.5%) whereas T. seperata was infrequent in sheep (2%) and rare in goats (0.4%). None of the animals were positive for Babesia spp.; however, Sarcocystis capracanis and S. tenella were detected in one goat and a sheep, respectively. The widespread distribution of Theileria spp. among cattle in northern Ethiopia including the virulent T. annulata and more mildly pathogenic T. mutans and T. orientalis, and the high infection rate in sheep with the usually sub-clinical T. ovis indicate extensive exposure to ticks and transmission of piroplasms with an important economic impact.

Studying the correlations among hematological and serum biochemical constituents in cattle theileriosis

The present study was undertaken to investigate the influence of tropical theileriosis on serum constituents, erythrocytes and platelets pictures and to study the correlation between the studied parameters. A total number of 26 cows were subjected to study. Out of them 16 cows were suffered from theileria infection. Comparing theileria infected group with the control group revealed significant decreases in total RBCS counts (p < 0.01), haemoglobin concentration (p < 0.01), packed cell volume (PCV) (p < 0.01), platelets count (PLT) (p < 0.01), plateletcrit (PCT) (p < 0.01), significant decreases in serum total proteins (p < 0.01), albumin (p < 0.01), calcium (p < 0.01), and phosphorus (p < 0.01) levels, and significant increases in serum blood urea nitrogen (BUN) (p < 0.05) and creatinine (p < 0.05) levels, and in serum aspartate aminotransferase (p < 0.01) and gamma glutamyl transferase (GGT) (p < 0.01) activities. Correlations between serum biochemical parameters revealed significant positive correlations between total proteins and albumin (r = 0.598*), A/G ratio and albumin (r = 0.860**), calcium and albumin (r = 0.729*), calcium and A/G ratio (r = 0.752*), GGT and BUN (r = 0.539*), and significant negative correlations between A/G ratio and globulins (r = -0.809**) and between glucose and albumin (r = -0.614*). Erythrocytes count showed a significant negative correlation with mean corpuscular volume (MCV) (r = -0.966**) and red blood cells distribution width (RDW) (r = -0.909**). MCV showed a significant positive correlation with RDW (r = 0.860*) and PCV (r = 0.781*). RDW was positively correlated with PCV (r = 0.966**). PLT count showed a significant positive correlation with mean platelet volume (MPV) (r = 0.992**), platelets distribution width (PDW) (r = 0.956**) and PCT (r = 0.994**). Furthermore, MPV showed a significant positive correlation with PDW (r = 0.940**) and a negative correlation with PCT (r = -0.974**). PDW was negatively correlated with PCT (r = -0.974**). It could be concluded that theileria infection in cattle resulted in anaemia, thrombocytopenia, hypoproteinaemia, hypoalbuminaemia and hypophosphataemia, in addition to hepatic and kidney dysfunction.

High-resolution genotyping and mapping of recombination and gene conversion in the protozoan Theileria parva using whole genome sequencing

BACKGROUND

Theileria parva is a tick-borne protozoan parasite, which causes East Coast Fever, a disease of cattle in sub-Saharan Africa. Like Plasmodium falciparum, the parasite undergoes a transient diploid life-cycle stage in the gut of the arthropod vector, which involves an obligate sexual cycle. As assessed using low-resolution VNTR markers, the crossover (CO) rate in T. parva is relatively high and has been reported to vary across different regions of the genome; non-crossovers (NCOs) and CO-associated gene conversions have not yet been characterised due to the lack of informative markers. To examine all recombination events at high marker resolution, we sequenced the haploid genomes of two parental strains, and two recombinant clones derived from ticks fed on cattle that had been simultaneously co-infected with two different parasite isolates.

RESULTS

By comparing the genome sequences, we were able to genotype over 64 thousand SNP markers with an average spacing of 127 bp in the two progeny clones. Previously unrecognized COs in sub-telomeric regions were detected. About 50% of CO breakpoints were accompanied by gene conversion events. Such a high fraction of COs accompanied by gene conversions demonstrated the contributions of meiotic recombination to the diversity and evolutionary success of T. parva, as the process not only redistributed existing genetic variations, but also altered allelic frequencies. Compared to COs, NCOs were more frequently observed and more uniformly distributed across the genome. In both progeny clones, genomic regions with more SNP markers had a reduced frequency of COs or NCOs, suggesting that the sequence divergence between the parental strains was high enough to adversely affect recombination frequencies. Intra-species polymorphism analysis identified 81 loci as likely to be under selection in the sequenced genomes.

CONCLUSIONS

Using whole genome sequencing of two recombinant clones and their parents, we generated maps of COs, NCOs, and CO-associated gene conversion events for T. parva. The data comprises one of the highest-resolution genome-wide analyses of the multiple outcomes of meiotic recombination for this pathogen. The study also demonstrates the usefulness of high throughput sequencing typing for detailed analysis of recombination in organisms in which conventional genetic analysis is technically difficult.

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.

Identification of Theileria parva and Theileria sp. (buffalo) 18S rRNA gene sequence variants in the African Buffalo (Syncerus caffer) in southern Africa

Theileria parva is the causative agent of Corridor disease in cattle in South Africa. The African buffalo (Syncerus caffer) is the reservoir host, and, as these animals are important for eco-tourism in South Africa, it is compulsory to test and certify them disease free prior to translocation. A T. parva-specific real-time polymerase chain reaction (PCR) test based on the small subunit ribosomal RNA (18S rRNA) gene is one of the tests used for the diagnosis of the parasite in buffalo and cattle in South Africa. However, because of the high similarity between the 18S rRNA gene sequences of T. parva and Theileria sp. (buffalo), the latter is also amplified by the real-time PCR primers, although it is not detected by the T. parva-specific hybridization probes. Preliminary sequencing studies have revealed a small number of sequence differences within the 18S rRNA gene in both species but the extent of this sequence variation is unknown. The aim of the current study was to sequence the 18S rRNA genes of T. parva and Theileria sp. (buffalo), and to determine whether all identified genotypes can be correctly detected by the real-time PCR assay. The reverse line blot (RLB) hybridization assay was used to identify T. parva and Theileria sp. (buffalo) positive samples from buffalo blood samples originating from the Kruger National Park, Hluhluwe-iMfolozi Park, the Greater Limpopo Transfrontier Park, and a private game ranch in the Hoedspruit area. T. parva and Theileria sp. (buffalo) were identified in 42% and 28%, respectively, of 252 samples, mainly as mixed infections. The full-length 18S rRNA gene of selected samples was amplified, cloned and sequenced. From a total of 20 sequences obtained, 10 grouped with previously published T. parva sequences from GenBank while 10 sequences grouped with a previously published Theileria sp. (buffalo) sequence. All these formed a monophyletic group with known pathogenic Theileria species. Our phylogenetic analyses confirm the distinction between Theileria sp. (buffalo) and T. parva and indicate the existence of a single group of T. parva and two Theileria sp. (buffalo) 18S rRNA gene variants in the African buffalo. Despite the observed variation in the full-length parasite 18S rRNA gene sequences, the area in the V4 hypervariable region where the RLB and real-time PCR hybridization probes were developed was relatively conserved. The T. parva specific real-time PCR assay was able to successfully detect all T. parva variants and, although amplicons were obtained from Theileria sp. (buffalo) DNA, none of the Theileria sp. (buffalo) 18S rRNA sequence variants were detected by the T. parva-specific hybridization probes.

Prevalence and genetic diversity of Babesia and Anaplasma species in cattle in Sudan

Disease prevalence studies are one of the most valuable tools to demonstrate the risk or impact of certain infections in local and global economies. The data obtained in these studies contribute to develop strategies for disease control. The present study aims to provide information about the prevalence of babesiosis and anaplasmosis in the northern regions of Sudan. Blood samples from four different states of Sudan were collected from apparently healthy cattle (n=692), DNA was extracted and the prevalence of Babesia and Anaplasma species was analyzed by PCR. The results confirmed the presence of Babesia bigemina, Babesia bovis and Anaplasma marginale in cattle in northern Sudan with overall prevalence rates of 4.0%, 1.9% and 6.1%, respectively. Statistical analysis revealed that the prevalence of B. bigemina, B. bovis and A. marginale varies significantly between Sudanese states as well as in different age groups, while gender seems not to have a significant effect on the prevalence of these pathogens among Sudanese cattle. The highest prevalence for B. bigemina was found in the Aljazirah State while the highest number of A. marginale positive samples was reported in River Nile.

Development and laboratory evaluation of a lateral flow device (LFD) for the serodiagnosis of Theileria annulata infection

Several DNA-based and serological tests have been established for the detection of Theileria annulata infection, including polymerase chain reaction, reverse line blot and loop-mediated isothermal amplification, indirect enzyme-linked immunosorbent assay (ELISA), and competitive ELISA. In this study, we have applied knowledge from the development and application of a recombinant protein-based indirect ELISA and competitive ELISA to establish a rapid test for point-of-care diagnosis of T. annulata infection in the field to be used by the veterinarian. For the development of a lateral flow test, the recombinantly expressed T. annulata surface protein (TaSP) was applied as the test antigen and anti-TaSP antiserum as the control line. TaSP antigen conjugated to colloidal gold particles was used as the detection system for visualization at the test line for the binding of anti-TaSP antibody present in the serum of infected animals. The developed test specifically detected antibodies in the serum of animals experimentally infected with T. annulata and showed no cross-reactivity with serum from animals infected with other tested bovine pathogens (Trypanosoma brucei, Anaplasma marginale, Babesia bigemina, Babesia bovis, and Theileria parva). Testing of field samples was compared to results obtained by other serological tests, resulting in a sensitivity and specificity of 96.3% and 87.5% compared to indirect fluorescence antibody test, 98.7% and 81.8% compared to indirect ELISA, and 100% and 47.6% compared to competitive ELISA. In conclusion, a rapid test for the detection of T. annulata infection (T. annulata lateral flow device, Ta-LFD) has been developed, which is easy to perform, delivers results to be read by the naked eye within 10 min, and is suitable for the detection of infection in field samples.

Molecular detection ofBabesiaspp. and other haemoparasitic infections of cattle in Maputo Province, Mozambique

Molecular detection ofBabesiaspecies in apparently healthy cattle within an endemic region was carried out in order to determine the prevalence of carriers and the geographical distribution ofBabesia bigeminaandBabesia bovisin Maputo Province, Mozambique. Samples from 477 animals at 5 localities were analysed using 2 techniques, the semi-nested hot-start PCR and the reverse line blot (RLB) assay. With the semi-nested hot-start PCR, detection ofB. bigeminaranged between 30% and 89%, and ofB. bovisbetween 27% and 83%. The RLB assay was comparatively less sensitive in this study and detection ofB. bovisranged from 0% to 17%, andB. bigeminawas not detected at all by this technique. Analysis of new sequences of the 18S rRNA gene revealed that the currentB. bigeminaRLB probe is not specific for the identification of isolates in Mozambique. The RLB assay, however, resulted in the detection of 8 other haemoparasite species belonging to the generaBabesia,Theileria,AnaplasmaandEhrlichia. 18S rRNA gene sequences from theTheileriaspp. were identified, and a phylogenic tree constructed with these sequences yielded a heterogeneousT. mutans-like group. In conclusion, infection withB. bigeminaandB. bovisis endemic in Maputo Province, but rates of transmission vary. Furthermore, mixed infections with the haemoparasites responsible for several tick-borne diseases in cattle are common in Mozambique.

A nested PCR assay exhibits enhanced sensitivity for detection of Theileria parva infections in bovine blood samples from carrier animals

Theileria parva causes East Coast fever, an economically important disease of cattle in sub-Saharan Africa. We describe a nested polymerase chain reaction (nPCR) assay for the detection of T. parva DNA in cattle blood spotted onto filter paper using primers derived from the T. parva-specific 104-kDa antigen (p104) gene. The sensitivity of this assay was compared to a previously described p104-based PCR and also the reverse line blot (RLB) technique, using serial dilutions of blood from a calf with known T. parva piroplasm parasitaemia. The relative sensitivities of the three assays were 0.4, 1.4 and 4 parasites/microl corresponding to blood parasitaemias of 9.2 x 10(-6)%, 2.8 x 10(-5)% and 8.3 x 10(-5)%, respectively. The three assays were applied to samples from two calves infected with the T. parva Muguga stock. Parasite DNA was consistently detectable by the two p104 PCR assays until 48 and 82 days post-infection, respectively, and thereafter sporadically. RLB detected parasite DNA in the two infected calves until days 43 and 45. Field samples from 151 Kenyan cattle exhibited 37.7% positivity for T. parva by regular p104 PCR and 42.3% positivity using p104 nPCR. Among 169 cattle blood samples from Southern Sudan, 36% were positive for T. parva using nPCR. The nPCR assay represents a highly sensitive tool for detection and monitoring of asymptomatic carrier state infections of T. parva in the blood of cattle.

Live immunization against East Coast fever--current status

The infection-and-treatment method (ITM) for immunization of cattle against East Coast fever has historically been used only on a limited scale because of logistical and policy constraints. Recent large-scale deployment among pastoralists in Tanzania has stimulated demand. Concurrently, a suite of molecular tools, developed from the Theileria parva genome, has enabled improved quality control of the immunizing stabilate and post-immunization monitoring of the efficacy and biological impact of ITM in the field. This article outlines the current status of ITM immunization in the field, with associated developments in the molecular epidemiology of T. parva.

Development and evaluation of a loop-mediated isothermal amplification method for diagnosis of tropical theileriosis

A loop-mediated isothermal amplification (LAMP) assay was developed and evaluated for diagnosis of tropical theileriosis. A set of six primers was designed based on the unique gene of Theileria annulata (Theileria annulata strain Ankara hypothetical protein (GeneDB TA04795). The protocol for the reaction was setup and the specificity and sensitivity of the assay were established. The specificity experiment showed that LAMP primers amplified T. annulata DNA successfully, while no amplification was seen for Theileria parva, Theileria mutans, Theileria sergenti, Theileria sinensis, Babesia bovis as well as bovine genomic DNA and water control. When the sensitivity of LAMP assay was compared with that of conventional PCR a 10-fold higher sensitivity was found, with a detection limit of 10 pg/microl of genomic DNA isolated from a T. annulata-infected cell line. The LAMP product was confirmed by restriction digestion and staining with SYBR Green I. Furthermore, the LAMP assay was applied for the diagnosis of T. annulata in field samples and compared with reverse line blot (RLB), demonstrating that results of the LAMP assay corresponded to those of RLB. These results indicate that the LAMP assay is rapid and simple to run, cost-effective, sensitive and specific and has potential usefulness for application in epidemiological studies on T. annulata infection of cattle.

Determination of potential risk factors associated with Theileria annulata and Theileria parva infections of cattle in the Sudan

A multi-variate logistic regression analysis was performed on two sets of data on the prevalence of Theileria annulata in Northern Sudan and Theileria parva in Southern Sudan, to determine the potential risk factors that might affect the distribution of the infections in those regions. The logistic regression model was fit with the tested risk factors for each disease, separately. The results indicated that locations, management systems and age could be held as risk factors for T. annulata infection in Northern Sudan, while for T. parva locations and seasons could be held as risk factors in Southern Sudan. The results of this study will assist in the development of more effective control strategies for smallholder dairy farms in the country.