Epidemiological and Biomolecular Studies on Echinococcus granulosusin Sudan

Abstract

This study represents an epidemiological and biomolecular study about Echinococcus spp. and hydatid disease in definitive and intermediate hosts including humans in Sudan. In this study, a survey of cystic echinococcosis was conducted duringthe period from May 2001 to July 2003 in different parts of the Sudan. The prevalence rates in camels, cattle, sheep and goats examined in different states of the Sudan was found to be 59.8% (466/779), 6.1% (299/4893), 11.3% (1180/10422) and 1.9% (106/5565) respectively. The encountered number of cysts was 2387 in camels, 333 in cattle, 1514 in sheep and 108 in goats. Fertility rates were found to be 73.7%, 77%, 19% and 31.5% in camel, cattle, sheep and goat respectively. The favorite site for cysts in camels was the lung (1627/2387). The liver was found to be the preferred site in cattle (206/333) whereas the peritoneum was the predilection site in sheep (1242/1514) and goats (53/108). Strain characterization of the E. granulosuscomplex in human and livestock population was described for the first time by using polymerase chain reaction amplification and sequencing technology. Even though we were able to detect E. ortleppiand sheep strain (G1) in some samples, camel strain (G6)appears to be the predominant strain causing cystic echinococcosis in humans and animals in Sudan. 533 of a total of 542 of all isolates were characterized as belonging to this strain. In this study, the sheep strain of E.granulosuswas reported for the first time in Sudan in two samples of human origin and five samples of sheep origin. Secondly, 42 dogs shot as a part ofthe rabies control program in Tamboul and Rofa, central Sudan, were autopsied and their intestinal contents were examinedfor the presence of Echinococcus worms. Faecal samples were taken for coprodiagnosis. Worm burden in positive dogs was determined using dilution method and the harvested worms were characterized using G5/6/7 and G1 PCRs. From the 42 euthanized dogs, 12 (28.5) were harboring E.granulosusworms The worm burden was 22-80*10 3 in the positive dogs. All the DNA samples extracted from the wormsuspension were characterized as camel (G6) strain of E.granulosus. 83.3% (10/12) of the DNA extracted from the faecal samples collected from the 12 dogs which were found to be positive at necropsy were also found positive with copro PCR and the strain was characterized as camel (G6) strain of E.granulosus. Two samples were consideredinconclusive as there was no signal in the inhibition test. 93.3% (28/30) copro DNA samples from the 30 samples collected from the dogs which were reported negative at necropsy were also negative using copro-diagnostic PCR. The other two samples were positive and characterized as sheep (G1) strain of E.granulosus. This copro PCR method was used for the first time in such a survey. Disregarding the inhibited samples, the overall sensitivity of the test was found to be 100%. For the purpose of this study, hydatid cysts were obtained from the lungs of naturally infected camels (Camelus dromedarius) in Tamboul slaughterhouse in central Sudan. Viable protoscolices were collected from these cysts and used for experimental infection of dogs at different doses. Ten dogs were divided into two groups (A and B) of five dogs each. Dogs in group A received a dose of 4×10 3 protoscolices eachwhereas dogs in group B received a dose of 8×10 3 .protoscolices each. Fecal samples were examined for patent infection during the study period. Dogs were necropsied at 45 dpi (group A) and 54 dpi (group B). Noeggs were detected in fecal samples from group A throughout the experimental period (45 days). However, eggs were first demonstratedin faeces 52 dpi in group B. The experimental animals in both groups did not show any adverse clinical signs during the experimental study. Echinococcus granulosus worms were recovered from both groups at the time of necropsy. Molecular characterization ofthe adult worms was made possible using the polymerase chain reaction (PCR)-based detection assay. The worms were identifiedas G6 (camel) strain of E. granulosus. It was found that the prepatency period in dogs after experimental infection with protoscolices of camel origin is longer than the reported for other strains of E.granulosus. These are the first data on prepatency periods of the camel strain G6 in dogs confirmed by molecular characterization