Prevalence of mixed Trypanosoma congolense infections in livestock and tsetse in KwaZulu-Natal, South Africa

K Gillingwater,M.V Mamabolo,P.O.A Majiwa

doi:10.4102/jsava.v81i4.151

Abstract

Trypanosoma congolense causes the most economically important animal trypanosomosis in Africa. In South Africa, a rinderpest pandemic of the 1890s removed many host animals, resulting in the near-eradication of most tsetse species. Further suppression was achieved through spraying with dichlorodiphenyltrichloroethane (DDT); however, residual populations of Glossina austeni and G. brevipalpis remained in isolated pockets. A total of 506 of these tsetse flies were captured in the Hluhluwe-iMfolozi Park, the St Lucia Wetland Park and Boomerang commercial farm. The polymerase chain reaction (PCR) was used to determine the infection rate and frequency of mixed infections of these flies. Additionally, 473 blood samples were collected from cattle at communal diptanks and a commercial farm in the area and each one examined by the haematocrit centrifugation technique (HCT). Furthermore, buffy coats from these blood samples were spotted onto FTA Elute cards and the DNA extracted from each one tested using 3 separate PCRs. The HCT revealed the presence of trypanosomes in only 6.6% of the blood samples; by contrast, species-specific PCR detected trypanosome DNA in 50% of the samples. The species-specific PCR detected trypanosome DNA in 17% of the tsetse flies, compared with the nested PCR targeting rDNA which detected trypanosome DNA in only 14% of the samples. Over time, the transmission of Savannah-type T. congolense and Kilifi-type T. congolense as mixed infections could have an impact on disease manifestation in different hosts in the area.

Highlights

Trypanosoma congolense, the smallest of the trypanosome species, remains the most pathogenic to animals[2]
473 samples were collected from cattle and examined using the haematocrit centrifugation technique (HCT) and polymerase chain reaction (PCR) targeting the 18S ribosomal RNA gene locus and the species-specific DNA sequences
Tsetse flies collected in the study area were predominantly G. brevipalpis, captured during early dawn and at dusk, compared with G. austeni, which were less abundant and appeared most active during daylight hours

Summary

Introduction

Trypanosoma congolense, the smallest of the trypanosome species, remains the most pathogenic to animals[2]. Tsetse-transmitted trypanosomes infective to livestock cause huge economic losses to the livestock industry[18] and tsetse flies (Glossina spp.) currently infest over 10 million square kilometres of fertile land distributed among 37 countries within the African continent. South Africa was fairly successful at controlling the spread of nagana; sleeping sickness, the equivalent disease in humans, has not been observed in the country. The tsetse populations declined drastically after rinderpest swept through the country in the 1890s and, combined with aggressive spraying with DDT, large areas such as the Kruger National Park were freed of the fly. Small isolated populations of tsetse survived in aAgricultural Research Council, Onderstepoort Veterinary Institute, Private Bag X05, Onderstepoort, 0110 South Africa.

Methods

Results

Conclusion