A slaughter slab survey for extra-intestinal porcine helminth infections in northern Tanzania.

A survey on extra-intestinal porcine helminths was conducted at three slaughter slabs that receive pigs from Mbulu, a district endemic for porcine cysticercosis in northern Tanzania. Seventy carcases of pigs between 1 and 2 years old were examined between December 1997 and March 1998. The examination involved ante-mortem lingual examination for Taenia solium cysticercosis followed by post-mortem inspection. In addition, a laboratory procedure was performed to determine whether any of these domestic pigs were infected with Trichinella species. Parasites detected were Ascaris suum (44.3%), Echinococcus granulosus (4.3%) and Taenia hydatigena (1.4%). The lack of cases of porcine cysticercosis in this study compared to previous studies suggests that pig traders are conducting their own ante-mortem lingual examinations before purchasing pigs in the rural communities where the parasite is still highly prevalent. It is concluded that improved meat inspection could prove useful in reducing the local population's risk of infection with these parasites. The results of this study have revealed the parasites of agricultral and public health importance in the targeted communities. Further epidemiological investigations are required to better determine parasite prevalence and impact in order to formulate appropriate and cost-effective strategies for control.

Risk factors for the prevalence of porcine cysticercosis in Mbulu District, Tanzania.

To estimate prevalence of and risk factors for the prevalence of porcine cysticercosis in Mbulu District, Tanzania, 770 live pigs were examined by lingual examination in 21 villages. Structured observations and questionnaire interviews were used to assess pig rearing practices and household use of latrines. Associations between factors were analyzed using a Bayesian hierarchical model to obtain prevalence odds ratio (OR) and 95% Bayesian Credible Intervals (95% BCI). Prevalence was 17.4% (village-specific range 3.2-46.7%). Prevalence of porcine cysticercosis was considerably higher in pigs reared in households lacking latrines than in those reared in households that were using latrines (OR = 2.04; 95% BCI = 1.25, 3.45). About 96% of the pigs were kept under free-range conditions. This study suggests the need for further studies in order to design and implement effective prevention and control measures for porcine cysticercosis in Mbulu District, Tanzania.

Prevalence of Cryptosporidium spp. oocysts in cattle and wildlife in Morogoro region, Tanzania.

Prevalences of Cryptosporidium spp. oocysts in cattle (n = 486) on five selected farms in Morogoro municipality and three species of herbivorous wildlife (n = 87) from Mikumi National Park, Morogoro, Tanzania, were determined using the modified Ziehl-Neelsen staining technique. Of 486 bovine faecal samples, 5.3% were positive for Cryptosporidium spp. The prevalence of Cryptosporidium was higher in calves less than 3 months of age compared to weaned calves and adults. Cryptosporidium spp. oocysts were detected in both diarrhoeic and non-diarrhoeic animals, but there was a significantly higher prevalence (P < 0.001) of oocyst shedding in diarrhoeic than in non-diarrhoeic animals. Of the 87 faecal specimens from the wildlife species, 36 were from the African buffaloes (Syncerus caffer), 25 from zebra (Equus zebra) and 26 from the wildebeest (Connochaetes gnou). Cryptosporidium spp. oocysts were detected in eight (22%) buffaloes, seven (28%) zebras and seven (27%) wildebeests. Confirmation of the diagnosis was performed using anti-Cryptosporidium monoclonal antibody specific for Cryptosporidium muris. Cryptosporidium parvum and Cryptosporidium baileyi (Pathasure Cryptosporidium test kit).

Experimental single and trickle infections of cattle with Taenia saginata: studies of immunodiagnosis.

Two groups of 12 calves were given either a single infection dose of 30,000 Taenia saginata eggs (group A) or trickle infected with 12 x 2500 T saginata eggs (group B). The calves were killed 16, 22 or 54 weeks after infection and the numbers of viable and dead parasites were counted by slicing selected organs and muscles of half of the carcases. The total numbers of cysts and the numbers of viable cysts were higher in group A than in group B. Within the two groups there were no significant differences between the numbers of cysts at the three dates of slaughter. Comparable results were obtained by using an ELISA and a dot blot procedure for the detection of antibody in the serum of the infected calves; an initial increase in response during the first 10 weeks after infection was generally followed by a gradual decline. When using a monoclonal antibody-based ELISA for the detection of circulating antigens, the sera from all the 14 animals which had no viable cysts or only dead cysts at slaughter did not react with the monoclonal antibodies. Calves 122 and 123, which harboured two and 122 viable cysts, respectively, reacted positively during the late phase of the infection to the antigen-detecting ELISA. However, several other animals which harboured between two and 41 viable cysts at slaughter did not react.

Immunodiagnosis of Taenia saginata in cattle using hydrophobic antigens from T. hydatigena metacestode cyst fluid.

Hydrophobic fractions isolated from cyst fluid of Taenia hydatigena metacestodes, obtained from naturally infected goats from Tanzania, were used in an indirect ELISA and in immunoblot (Western or dot blot) procedures. The use of the most hydrophobic fractions of the cyst fluid proved to result in a better diagnostic discrimination in ELISA than the more hydrophilic fractions. Best diagnostic ratio between responses from T. saginata infected and non-infected cattle was achieved when using horse-radish peroxidase-labelled sheep antibovine IgG1 as the conjugate. When the hydrophobic fractions of T. hydatigena cyst fluid were employed as antigen in ELISA, no cross-reaction took place with sera from cattle infected with Fasciola hepatica, Ostertagia ostertagi, Cooperia oncophora, Dictyocaulus viviparus, Sarcocystis cruzi or a mixture of D. viviparus, Trichostrongylus axei and Eimeria. Using the Western blot technique, specific low molecular weight components (M(r) 10-18 kDa) of the hydrophobic fractions of the cyst fluid were reactive with sera from 14 of the 21 calves infected with T. saginata for 60 days. Also, hydrophobic fractions of T. hydatigena cyst fluid were dotted onto strips of filter membranes and reacted specifically with sera from 21 calves infected with T. saginata. This technique resulted in the highest sensitivity, detecting 17 of the 21 calves infected with T. saginata. Calves harbouring as few as 16, 26, 43, 53 and 74 cysts could be detected. Thirteen calves harbouring between 74 and 2,545 cysts were all detected. However, 4 calves harbouring 2, 22, 52 and 66 cysts, respectively, were not detected. The potential of using a dot blot technique in large scale investigations in the tropics is present. However, before accepting any of the three tests in the tropical environment, a broader spectrum of helminth infections should be evaluated for their eventual cross-reactivity.