Genetic Diversity of African Trypanosomes in Tsetse Flies and Cattle From the Kafue Ecosystem

Prevalence and Association of Trypanosomes and Sodalis glossinidius in Tsetse Flies from the Kafue National Park in Zambia

Tsetse flies are obligate hematophagous vectors of animal and human African trypanosomosis. They cyclically transmit pathogenic Trypanosoma species. The endosymbiont Sodalis glossinidius is suggested to play a role in facilitating the susceptibility of tsetse flies to trypanosome infections. Therefore, this study was aimed at determining the prevalence of S. glossinidius and trypanosomes circulating in tsetse flies and checking whether an association exists between trypanosomes and Sodalis infections in tsetse flies from Kafue National Park in Zambia. A total of 326 tsetse flies were sampled from the Chunga and Ngoma areas of the national park. After DNA extraction was conducted, the presence of S. glossinidius and trypanosome DNA was checked using PCR. The Chi-square test was carried out to determine whether there was an association between the presence of S. glossinidius and trypanosome infections. Out of the total tsetse flies collected, the prevalence of S. glossinidius and trypanosomes was 21.8% and 19.3%, respectively. The prevalence of S. glossinidius was 22.2% in Glossina morsitans and 19.6% in Glossina pallidipes. In relation to sampling sites, the prevalence of S. glossinidius was 26.0% in Chunga and 21.0% in Ngoma. DNA of trypanosomes was detected in 18.9% of G. morsitans and 21.4% of G. pallidipes. The prevalence of trypanosomes was 21.7% and 6.0% for Ngoma and Chunga, respectively. The prevalences of trypanosome species detected in this study were 6.4%, 4.6%, 4.0%, 3.7%, 3.1%, and 2.5% for T. vivax, T. simiae, T. congolense, T. godfreyi, T. simiae Tsavo, and T. b. brucei, respectively. Out of 63 trypanosome infected tsetse flies, 47.6% of the flies also carried S. glossinidius, and the remaining flies were devoid of S. glossinidius. A statistically significant association was found between S. glossinidius and trypanosomes (p < 0.001) infections in tsetse flies. Our findings indicated that presence of S. glossinidius increases the susceptibility of tsetse flies to trypanosome infections and S. glossinidius could be a potential candidate for symbiont-mediated vector control in these tsetse species.

Comparison of ITS-1 and TBR-1/2 primer sensitivity for the detection of Trypanosoma evansi local isolates in experimental rats using a polymerase chain reaction

Background and Aim:

Surra is caused by Trypanosoma evansi. The detection method using conventional parasitological tests has not always shown positive results in blood parasite detection, although the livestock has presented with clinical signs. Therefore, a fast and accurate diagnosis is necessary to prevent the disease predominately in field isolates. This study aimed to investigate the sensitivity of molecular detection method using two different specific primers, namely, Internal Transcribed Spacer 1 (ITS-1) and Trypanosoma brucei repeat 1/2 (TBR-1/2) against T. evansi field isolates from Banten Province, Indonesia.

Materials and Methods:

The isolates of T. evansi used in this study were collected from Banten Province and cultured and preserved by the National Research Center for Veterinary Science, Indonesia. Eighteen experimental rats were divided into three equal groups, which were categorized as control, 1 × 10¹, and 1 × 10⁴ infective doses. The isolates were injected into all experimental albino rats intraperitoneally. All samples were tested using conventional blood smear, card agglutination test (CATT), and polymerase chain reaction (PCR) method.

Results:

The results of the CATT examination in all treatments showed negative results. However, PCR results showed that two different primers, namely, ITS-1 and TBR-1/2 had been successfully detected T. evansi from infected experimental rats, proven by positive PCR band appeared in 480 base pairs (bp) and 164 bp, respectively.

Conclusion:

Based on the molecular diagnostic test using PCR method, TBR-1/2 primer is more sensitive to detect T. evansi compared to ITS-1 primer. The present finding provides preliminary data for studying the efficiency of different primers if practically applied as a standard diagnostic test for trypanosomiasis, especially in Indonesian livestock.

Prevalence of trypanosomes and selected symbionts in tsetse species of eastern Zambia

Insect symbionts have attracted attention for their potential use as anti-parasitic gene products in arthropod disease vectors. While tsetse species of the Luangwa valley have been extensively studied, less is known about the prevalence of symbionts and their interactions with the trypanosome parasite. Polymerase chain reaction was used to investigate the presence of Wolbachia and Sodalis bacteria, in tsetse flies infected with trypanosomes (Trypanosoma vivax, Trypanosoma congolense and Trypanosoma brucei). Out of 278 captured tsetse flies in eastern Zambia, 95.3% (n = 265, 95% CI = 92.8–97.8) carried endosymbionts: Wolbachia (79.1%, 95% CI 73.9–83.8) and Sodalis (86.3%, 95% CI 81.7–90.1). Overall, trypanosome prevalence was 25.5% (n = 71, 95% CI = 20.4–30.7), 10.8% (n = 30, 95% CI 7.1–14.4) for T. brucei, 1.4% (n = 4, 95% CI = 0.4–3.6) for both T. congolense and T. vivax, and 0.7% (n = 2, 95% CI 0.1–2.6) for T. b. rhodesiense. Out of 240 tsetse flies that were infected with Sodalis, trypanosome infection was reported in 40 tsetse flies (16.7%, 95% CI = 12.0–21.4) while 37 (16.8%, 95% CI 11.9–21.8) of the 220 Wolbachia infected tsetse flies were infected with trypanosomes. There was 1.3 times likelihood of T. brucei infection to be present when Wolbachia was present and 1.7 likelihood of T. brucei infection when Sodalis was present. Overall findings suggest absence of correlation between the presence of tsetse endosymbionts and tsetse with trypanosome infection. Lastly, the presence of pathogenic trypanosomes in tsetse species examined provided insights into the risk communities face, and the importance of African trypanosomiasis in the area.

Development of Cathepsin L-like Real-Time PCR Assays for the Detection of African Animal Trypanosomosis (AAT) in South Africa

African animal trypanosomosis (AAT), is an infectious parasitic disease of wildlife and livestock caused by multiple species and strains of Trypanosoma. In South Africa, it is restricted to northern KwaZulu-Natal (NKZN) and caused by Trypanosoma congolense and Trypanosoma vivax. A cross-sectional study was done to determine AAT prevalence in 384 goat samples and identify trypanosome species circulating in 60 cattle at dip tanks that are on the interface with the Hluhluwe-uMfolozi game reserve in NKZN. Both cattle and goat samples were analyzed using the buffy coat technique (BCT) and a polymerase chain reaction (PCR) assay targeting the internal transcribed spacer 1 (ITS) region. Cattle samples were further analyzed using an ITS quantitative real-time PCR (qPCR) assays designed for the detection of T. congolense, T. vivax, and T. brucei. None of the goat samples tested positive for Trypanosoma infections. The ITS qPCR assay detected Trypanosoma DNA in 30% of the cattle samples, while only 8.3% were positive with the ITS PCR and 11.7% were positive using BCT. Quantitative real-time PCR assays were designed to amplify a 98 bp, 137 bp, and 116 bp fragment of the cathepsin L-like (CATL) gene from T. brucei, T. theileri, and T. congolense, respectively. Each assay was shown to be efficient (>94%) and specific (10⁹ to 10²/10¹ copies/reaction) in the detection of Trypanosoma species. The CATL qPCR assays detected T. congolense and T. theileri infections in 33.3% of the cattle samples. The CATL qPCR assays also detected T. congolense infections in goats (23.1%) that were neither detected by BCT nor the ITS PCR. The CATL qPCR assays provide an additional, sensitive, and specific tool for Trypanosoma diagnostics. The presence of trypanosomes in goats suggests they might be potential reservoirs of infections to other livestock.

Evidence of Borrelia theileri in Wild and Domestic Animals in the Kafue Ecosystem of Zambia

Members of the genus Borrelia are arthropod-borne spirochetes that are human and animal pathogens. Vertebrate hosts, including wild animals, are pivotal to the circulation and maintenance of Borrelia spirochetes. However, information on Borrelia spirochetes in vertebrate hosts in Zambia is limited. Thus, we aimed to investigate the presence of Borrelia spirochetes in wild animals and cattle in Zambia. A total of 140 wild animals of four species and 488 cattle DNA samples from /near the Kafue National Park were collected for real-time PCR screening, followed by characterization using three different genes with positive samples. Five impalas and 20 cattle tested positive using real-time PCR, and sequence analysis revealed that the detected Borrelia were identified to be Borrelia theileri, a causative agent of bovine borreliosis. This is the first evidence of Borrelia theileri in African wildlife and cattle in Zambia. Our results suggest that clinical differentiation between bovine borreliosis and other bovine diseases endemic in Zambia is required for better treatment and control measures. As this study only included wild and domestic animals in the Kafue ecosystem, further investigations in other areas and with more wildlife and livestock species are needed to clarify a comprehensive epidemiological status of Borrelia theileri in Zambia.

Molecular characterization of Trypanosoma vivax in tsetse flies confirms the presence of the virulent Tvv4 genotype in Kenya: Potential implications for the control of trypanosomiasis in Shimba Hills

Trypanosoma vivax is a vector-borne protozoan parasite of livestock endemic to Africa and South America. To date, fifteen genotypes of the parasite have been described in vertebrate and insect hosts in East Africa. However, information regarding T. vivax diversity remains limited in many endemic countries in the sub-region, including Kenya. Such information could deepen insight into the local epidemiology of animal trypanosomiasis in Shimba Hills, a wildlife area in southeast Kenya where T. vivax is endemic and infects livestock. We employed two-gene conventional-PCR-sequencing and phylogenetic analysis to characterize T. vivax genotypes in tsetse flies collected between November 2018 and September 2019 in the wildlife-livestock interface of the Shimba Hills National Reserve. Phylogenetic analysis of Internal Transcribed Spacer-1 (ITS-1) sequences of T. vivax isolates confirmed the presence of two T. vivax genotypes in Shimba Hills of which >80% of T. vivax isolates from tsetse flies clustered within the virulent Tvv4-genotype clade. Tsetse infections with the Tvv4 genotype were also confirmed based on 18S rRNA gene sequencing. Expanded gene characterization identified three closely related haplotypes within the Tvv4-clade. The Tvv4-isolates were detected in male and female Glossina pallidipes tsetse flies, most of which were collected from grasslands and within two kilometres of the Shimba Hills National Reserve boundary. Considering that T. vivax is the most common trypanosome in the Shimba Hills area and causes severe clinical conditions in livestock, the Tvv4 genotype reported here for the first time in Kenya contributes to our understanding of these pathologies. The effectiveness of trypanocidal drugs in the management of Tvv4 is presently not clearly understood. Therefore, the parasite management in Shimba Hills should focus on vector control to reduce the density of G. pallidipes, especially in grasslands near the wildlife protectorate.