Molecular epidemiology of camel trypanosomiasis based on ITS1 rDNA and RoTat 1.2 VSG gene in the Sudan

Trypanosome infection in dromedary camels in Eastern Ethiopia: Prevalence, relative performance of diagnostic tools and host related risk factors

A cross-sectional study was conducted in Chifra and Dewe districts of Afar region, Eastern Ethiopia, to determine the prevalence, agreement between diagnostic tests and host related risk factors of trypanosome infection in camel. An overall prevalence of 2%, 24.1%, 21.3%, 9.5% and 7.8% was recorded with respectively Giemsa stained thin blood smear, CATT/T. evansi, RoTat1.2 PCR, 18S PCR and ITS-1PCR in a cohort of 399 animals. Only one T. vivax infection was confirmed by TvPRAC PCR indicating T. evansi as the predominant species affecting camels in the study area. No single animal was positive when tested with T. evansi type B specific EVAB PCR. There was slight agreement between the CATT/T. evansi and the molecular tests. Among the PCR methods, RoTat 1.2 PCR yielded a significantly higher positivity rate compared to 18S PCR and ITS-1 PCR. There was no significant difference in the positivity rate observed in each gender of camels (p>0.05). The positivity rate was significantly higher in camels with poor body condition and in older animals when tested using the CATT/T.evansi or RoTat 1.2 PCR (p>0.05). Camels that tested positive with all tests had significantly lower PCV's (p<0.05). This study provides further evidence that T. evansi is endemic in the Afar region of Ethiopia. The latent class analysis indicated an estimate overall prevalence of 19% (95% CI: 13-28). Moreover, the model indicated low sensitivity of CATT/T. evansi (43%) and the PCR tests (39-53%) but higher specificity of the PCR tests (86-99%) and low specificity of CATT/T. evansi (80%). This study suggests that improved sensitivity and reliability of the tests would help diagnosis of trypanosomosis. Further studies are required to determine the prevalence of clinical disease and losses due to trypanosomosis.

Epidemiology of Trypanosoma evansi and Trypanosoma vivax in domestic animals from selected districts of Tigray and Afar regions, Northern Ethiopia

Background

African animal trypanosomosis, transmitted cyclically by tsetse flies or mechanically by other biting flies, causes serious inflictions to livestock health. This study investigates the extent of non-tsetse transmitted animal trypanosomosis (NTTAT) by Trypanosoma (T.) evansi and T. vivax in domestic animals in the tsetse-free regions of Northern Ethiopia, Afar and Tigray.

Methods

A cross sectional study was conducted on 754 dromedary camels, 493 cattle, 264 goats, 181 sheep, 84 donkeys, 25 horses and 10 mules. The microhaematocrit centrifugation technique was used as parasitological test. Plasma was collected for serodiagnosis with CATT/T.evansi and RoTat 1.2 immune trypanolysis (ITL) while buffy coat specimens were collected for molecular diagnosis with T. evansi type A specific RoTat 1.2 PCR, T. evansi type B specific EVAB PCR and T. vivax specific TvPRAC PCR.

Results

The parasitological prevalence was 4.7% in Tigray and 2.7% in Afar and significantly higher (z = 2.53, p = 0.011) in cattle (7.3%) than in the other hosts. Seroprevalence in CATT/T.evansi was 24.6% in Tigray and 13.9% in Afar and was significantly higher (z = 9.39, p < 0.001) in cattle (37.3%) than in the other hosts. On the other hand, seroprevalence assessed by ITL was only 1.9% suggesting cross reaction of CATT/T.evansi with T. vivax or other trypanosome infections. Molecular prevalence of T. evansi type A was 8.0% in Tigray and in Afar and varied from 28.0% in horses to 2.2% in sheep. It was also significantly higher (p < 0.001) in camel (11.7%) than in cattle (6.1%), donkey (6%), goat (3.8%), and sheep (2.2%). Four camels were positive for T. evansi type B. Molecular prevalence of T. vivax was 3.0% and was similar in Tigray and Afar. It didn’t differ significantly among the host species except that it was not detected in horses and mules.

Conclusions

NTTAT caused by T. vivax and T. evansi, is an important threat to animal health in Tigray and Afar. For the first time, we confirm the presence of T. evansi type B in Ethiopian camels. Unexplained results obtained with the current diagnostic tests in bovines warrant particular efforts to isolate and characterise trypanosome strains that circulate in Northern Ethiopia.

First report of surra (Trypanosoma evansi infection) in a Tunisian dog

Trypanosoma evansi, the agent of surra, is a salivarian trypanosome, originating from Africa. Surra is a major disease in camels, equines and dogs, in which it can often be fatal in the absence of treatment. Animals exhibit nonspecific clinical signs (anaemia, loss of weight and abortion). In the present survey, a blood sample was collected in Sousse (Central Tunisia) from a dog that presented clinical signs of trypanosomiasis. Giemsa-stained blood smears and PCR were performed. ITS1 sequences from blood had 99.8 and 99.5% homology with published T. evansi sequences from cattle and camels, respectively. To our knowledge, this is the first report of T. evansi in a Tunisian dog.

Variant surface glycoproteins from Venezuelan trypanosome isolates are recognized by sera from animals infected with either Trypanosoma evansi or Trypanosoma vivax

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Soluble forms of VSGs from seven Venezuelan animal trypanosomes were purified and characterized.

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All purified soluble VSGs exhibited cross-reactivity with Trypanosoma vivax.

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Anti-VSG antibodies behaved as markers of infection for non-tsetse transmitted trypanosomes.

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All purified soluble VSGs can be used as diagnostic reagents for bovine trypanosomosis.

Salivarian trypanosomes sequentially express only one variant surface glycoprotein (VSG) on their cell surface from a large repertoire of VSG genes. Seven cryopreserved animal trypanosome isolates known as TeAp-ElFrio01, TEVA1 (or TeAp-N/D1), TeGu-N/D1, TeAp-Mantecal01, TeGu-TerecayTrino, TeGu-Terecay03 and TeGu-Terecay323, which had been isolated from different hosts identified in several geographical areas of Venezuela were expanded using adult albino rats. Soluble forms of predominant VSGs expressed during the early infection stages were purified and corresponded to concanavalin A-binding proteins with molecular masses of 48–67 kDa by sodium dodecyl sulfate-polyacrylamide gel electropohoresis, and pI values between 6.1 and 7.5. The biochemical characterization of all purified soluble VSGs revealed that they were dimers in their native form and represented different gene products. Sequencing of some of these proteins yielded peptides homologous to VSGs from Trypanosoma (Trypanozoon) brucei and Trypanosoma (Trypanozoon) evansi and established that they most likely are mosaics generated by homologous recombination. Western blot analysis showed that all purified VSGs were cross-reacting antigens that were recognized by sera from animals infected with either T. evansi or Trypanosoma (Dutonella) vivax. The VSG glycosyl-phosphatidylinositol cross-reacting determinant epitope was only partially responsible for the cross-reactivity of the purified proteins, and antibodies appeared to recognize cross-reacting conformational epitopes from the various soluble VSGs. ELISA experiments were performed using infected bovine sera collected from cattle in a Venezuelan trypanosome-endemic area. In particular, soluble VSGs from two trypanosome isolates, TeGu-N/D1 and TeGu-TeracayTrino, were recognized by 93.38% and 73.55% of naturally T. vivax-infected bovine sera, respectively. However, approximately 70% of the sera samples did not recognize all seven purified proteins. Hence, the use of a combination of various VSGs for the diagnosis of animal trypanosomosis is recommended.

Current status of equine piroplasmosis in the Sudan

This is a cross-sectional molecular epidemiological study on equine piroplasmosis (EP) affecting horses and donkeys in the Sudan. The study evaluated 499 samples from geographically distinct regions in eastern, central and western parts of the country. PCR amplification of the 18S rRNA gene of both Thelieria equi and Babesia caballi was carried out. Horses from all sampled areas were found positive to T. equi DNA but no B. caballi was detected. Absence of B. caballi infection was confirmed by another PCR targeting the B. caballi 48-kDa merozoite antigen. The overall prevalence was found to be 35.95%. The highest prevalence was detected in Showak 13 (81.3%) and the lowest was in Shearia locality in South Darfur 1 (5.6%). In another experiment, capillary electrophoresis was used to detect and differentiate between T. equi and B. caballi using one set of primers designed to amplify the 18S rRNA gene in a single PCR. Capillary electrophoresis method was found to be powerful in detecting mixed infections in artificially mixed controls samples. The data obtained in this study would contribute to the development of a national control strategy of EP in the Sudan.

Molecular epidemiological studies on animal trypanosomiases in Ghana

Background

African trypanosomes are extracellular protozoan parasites that are transmitted between mammalian hosts by the bite of an infected tsetse fly. Human African Trypanosomiasis (HAT) or sleeping sickness is caused by Trypanosoma brucei rhodesiense or T. brucei gambiense, while African Animal Trypanosomiasis (AAT) is caused mainly by T. vivax, T. congolense, T. simiae,T. evansi and T. brucei brucei. Trypanosomiasis is of public health importance in humans and is also the major constraint for livestock productivity in sub-Saharan African countries. Scanty information exists about the trypanosomiasis status in Ghana especially regarding molecular epidemiology. Therefore, this study intended to apply molecular tools to identify and characterize trypanosomes in Ghana.

Methods

A total of 219 tsetse flies, 248 pigs and 146 cattle blood samples were collected from Adidome and Koforidua regions in Ghana in 2010. Initial PCR assays were conducted using the internal transcribed spacer one (ITS1) of ribosomal DNA (rDNA) primers, which can detect most of the pathogenic trypanosome species and T. vivax-specific cathepsin L-like gene primers. In addition, species- or subgroup-specific PCRs were performed for T. b. rhodesiense, T. b. gambiense, T. evansi and three subgroups of T. congolense.

Results

The overall prevalence of trypanosomes were 17.4% (38/219), 57.5% (84/146) and 28.6% (71/248) in tsetse flies, cattle and pigs, respectively. T. congolense subgroup-specific PCR revealed that T. congolense Savannah (52.6%) and T. congolense Forest (66.0%) were the endemic subgroups in Ghana with 18.6% being mixed infections. T. evansi was detected in a single tsetse fly. Human infective trypanosomes were not detected in the tested samples.

Conclusion

Our results showed that there is a high prevalence of parasites in both tsetse flies and livestock in the study areas in Ghana. This enhances the need to strengthen control policies and institute measures that help prevent the spread of the parasites.

Prevalence of Trypanosoma evansi in horses in Israel evaluated by serology and reverse dot blot

Trypanosoma evansi is the cause of surra in horses, camels and other domestic animals. Following the first outbreak of surra in horses and camels in Israel in 2006, a survey of the prevalence of the parasite in the Israeli horse population was conducted using serology, PCR followed by the reverse dot blot (RDB) technique and blood smear microscopy. In total, 614 horses from 7 regions were sampled. The CATT/T. evansi kit was used for serology for all the horses. Horses from the Arava and Dead Sea region, where the first outbreak occurred, were sampled again one year later and both samples were subjected to serology and the RDB technique. The country wide seroprevalence was 4.6% (28/614). The seroprevalence in the Arava and Dead Sea region was 6.5% (9/139) in the first sampling compared with 4.1% (5/122) in the second, whereas the prevalence of RDB-positivity was 18.7% (26/139) in the first sampling and only 0.8% (1/122) in the second. All horses were asymptomatic except for one horse from the Arava and Dead Sea region that demonstrated clinical signs of surra combined with positive serology and RDB. The results of this study indicated that surra is prevalent in most regions of the country and thus should be considered an important differential diagnosis in horses and other domestic animals in Israel with chronic weight loss, edema or neurological signs.

Population genetics of Trypanosoma evansi from camel in the Sudan

Genetic variation of microsatellite loci is a widely used method for the analysis of population genetic structure of microorganisms. We have investigated genetic variation at 15 microsatellite loci of T. evansi isolated from camels in Sudan and Kenya to evaluate the genetic information partitioned within and between individuals and between sites. We detected a strong signal of isolation by distance across the area sampled. The results also indicate that either, and as expected, T. evansi is purely clonal and structured in small units at very local scales and that there are numerous allelic dropouts in the data, or that this species often sexually recombines without the need of the “normal” definitive host, the tsetse fly or as the recurrent immigration from sexually recombined T. brucei brucei. Though the first hypothesis is the most likely, discriminating between these two incompatible hypotheses will require further studies at much localized scales.

Trypanosomiasis due to Trypanosoma evansi is a widely distributed disease of livestock, affecting especially camelids and equines and is transmitted by biting flies. The disease is of great concern to many developing countries such as Sudan, where its large camel population estimated at over 4.6 million heads is at risk. It is generally believed that T. evansi has evolved when camels infected with T. brucei moved to tsetse-free areas, but only a few studies have been carried out to elucidate the genetic make-up of T. evansi. Therefore, in the current study, 15 microsatellite markers from non-coding loci on 38 isolates of T. evansi originating from different locations in Sudan were analyzed. Three reference strains from Sudan and Kenya were additionally analyzed and compared to the recent isolates. The results of this study revealed a highly significant isolation by distance pattern with rather small neighborhood sizes. It also suggested that T. evansi is either purely clonal with numerous problems of allelic dropouts or that it often sexually recombines without the need of the definitive host, the tsetse fly, or as the result of recurrent immigration from sexually recombined T. brucei brucei mutants.

An outbreak of bovine trypanosomiasis in the Blue Nile State, Sudan

Background

In this paper, we report an outbreak of bovine trypanosomiasis in Kurmuk District, Blue Nile State, Sudan that involved an infection with four Trypanosoma species in cattle. The outbreak occurred in June 2010 when indigenous cattle, mainly Kenana and Fulani breed types, crossed the national Sudanese border to Ethiopia and returned. A veterinarian was notified of massive deaths in the cattle populations that recently came from Ethiopia. All animals involved in the outbreak were from the nomadic Fulani group and resident local cattle were not infected and no death has been reported among them. A total of 210 blood samples were collected from the ear vein of cattle. A few samples were also collected from other domestic animals species. Parasitological examinations including hematocrit centrifugation techniques (HCT) and Giemsa-stained thin blood films were carried out. ITS1-PCR, which provides a multi-species-specific diagnosis in a single PCR, was performed.

Findings

Parasitological examinations revealed that 43% (91/210) of the affected cattle population was infected with two morphologically distinct trypanosomes. Seventy animals (33.3%) were infected with T. vivax and twenty one (10%) with T. congolense. In contrast, ITS1-PCR was able to identify four Trypanosoma species namely T. vivax, T. congolense, T. simiae and T. brucei in 56.7% (80/141). T. brucei showed the highest prevalence of 36.9% (52/141) and the lowest 19% (27/141) was displayed by T. congolense. Furthermore, and because ITS1-PCR could not differentiate between T. brucei subspecies, serum resistance-associated (SRA) gene based PCR was used to detect the human T. brucei rhodesiense in T. brucei positive samples. None of the samples was shown positive for T. b. rhodesiense. The identity of the 400 bp PCR product originating from T. simiae, was further confirmed by sequencing and subsequent phylogenetic analysis.

Conclusions

The outbreak of bovine trypanosomiasis occurred in the Blue Nile State was caused by mixed infection of two or more Trypanosoma species and the conventional parasitological examinations were not reliable in identifying all the species of Trypanosoma involved in the outbreak. It is difficult to determine the cause of the disease for the reason that the current enzootic situation in the resident cattle in the region is poorly understood. The study concluded that there are at least four species of trypanosomes that caused this outbreak in the Blue Nile State. The presence of mixed infections might have exacerbated the severity of the disease. It is hypothesized that variant parasite type(s) might have been introduced to Sudanese cattle when they crossed to Ethiopia, a tsetse belt region.

The best practice for preparation of samples from FTA®cards for diagnosis of blood borne infections using African trypanosomes as a model system

Background

Diagnosis of blood borne infectious diseases relies primarily on the detection of the causative agent in the blood sample. Molecular techniques offer sensitive and specific tools for this although considerable difficulties exist when using these approaches in the field environment. In large scale epidemiological studies, FTA^®cards are becoming increasingly popular for the rapid collection and archiving of a large number of samples. However, there are some difficulties in the downstream processing of these cards which is essential for the accurate diagnosis of infection. Here we describe recommendations for the best practice approach for sample processing from FTA^®cards for the molecular diagnosis of trypanosomiasis using PCR.

Results

A comparison of five techniques was made. Detection from directly applied whole blood was less sensitive (35.6%) than whole blood which was subsequently eluted from the cards using Chelex^®100 (56.4%). Better apparent sensitivity was achieved when blood was lysed prior to application on the FTA cards (73.3%) although this was not significant. This did not improve with subsequent elution using Chelex^®100 (73.3%) and was not significantly different from direct DNA extraction from blood in the field (68.3%).

Conclusions

Based on these results, the degree of effort required for each of these techniques and the difficulty of DNA extraction under field conditions, we recommend that blood is transferred onto FTA cards whole followed by elution in Chelex^®100 as the best approach.