Epidemiological survey of swine cysticercosis using ante-mortem and post-mortem examination tests in the southern highlands of Tanzania.

Pig keeping is known to be popular in the regions of the southern highlands zone (Mbeya, Iringa and Ruvuma) of Tanzania where more than 60% of pigs under the small-scale production system are raised. However, no epidemiological surveys on porcine cysticercosis have been conducted in the zone in spite of unofficial reports indicating the disease to be a widespread problem. To estimate prevalence rates and risk factors for porcine cysticercosis in Chunya and Iringa Rural Districts and Ruvuma Region (Songea and Mbinga Districts), 722, 808 and 302 live pigs, respectively, were examined by lingually and the prevalence of swine cysticercosis was found to be 7.6%, 8.4% and 16.9% for Chunya and Iringa Rural Districts, and Ruvuma Region, respectively. Structured observations and questionnaire interviews were used to analyse pig rearing practices and household use of latrines in Chunya and Iringa Rural Districts only. The analysis of effect of pig management practices, lack of a latrine, eating undercooked pork, home slaughter and no inspection of pork and lack of knowledge of T. solium on their association to tongue positivity in pigs was done by means of a contingency table. Odds ratios (OR) with corresponding 95% confidence intervals (95% CI) and p-values were calculated. Structured questionnaire interviews identified factors associated with the disease prevalence in both Chunya and Iringa Rural Districts were free-ranging of pigs, home slaughtering of pigs and pork not being inspected. While in Chunya and Iringa Rural Districts lack of latrine and barbecuing were found a risk factor, respectively. To control the disease in the study areas of the southern highlands there is a need for significant improvements regarding the use of latrines, confinement of pigs, pork inspection and thorough cooking of pork.

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.

Distribution and density of cysticerci of Taenia solium by muscle groups and organs in naturally infected local finished pigs in Tanzania.

The distribution and density of cysticerci of Taenia solium among distinct carcass sites was determined in 24 naturally infected finished pigs from Mbulu district, Tanzania. The heart, tongue, internal and external masseters, triceps brachii, lungs, liver, kidneys, psoas, diaphragm and brain of each pig as well as the muscles from the forelimb, hind limb, abdomen, head and thorax from one half of each pig carcass were all designated as distinct carcass sites and sliced in such a way that all fully developed cysts could be revealed and enumerated (i.e. each slice was less than 0.5 cm thick). The carcasses harboured from 76 to 80,340 cysts in total. Carcass sites which harboured the highest proportion of cysts were those of the hind and forelimbs (mean: 27.7 and 24.5%, respectively, of the total cysts in the carcass), while lower proportions were found in the tongue, heart, triceps brachii, and diaphragm (7, 3.6, 2 and 2, respectively). Relative cyst density was calculated for the different carcass sites by dividing the mean proportion of the total weight of the tissue groups into the mean proportion of cysts located in that site. The cysticerci in the examined distinct carcass sites were found in the following order of relative density: psoas muscles (10.5), internal masseter (8.1), external masseter (7.1), triceps brachii (4.9), forelimb (4.0), head muscles (3.8), tongue (3.4), hind limb (3.2), diaphragm (2.4), heart (1.9), abdominal muscles (1.3), trunk muscles (1.1), brain (1.0) and oesophagus (0.3). The proportion of cysts expected to be found at the surfaces exposed by visual examination or incision at meat inspection was calculated using an indirect method, which incorporated the area revealed by incision and visual inspection of an organ and the proportion of cysts located in the particular organ. It was estimated that 10.6% of the cysts would be located at inspected sites if regulations were followed carefully.

Comparison of worm control strategies in grazing sheep in Denmark.

Control of nematode parasites with reduced reliance on the use of anthelmintics was studied in 16 ewes with suckling twin lambs on contaminated pasture in Denmark. Ewes and lambs were treated with albendazole at turn-out 3 May. Ewes were removed from the groups on 26 July, and lambs were slaughtered on 11 October. The animals were allocated to 4 groups of 8 lambs and their 4 ewes. Group TS was treated with albendazole at weeks 3, 6 and 8 after turnout and set-stocked; group TM was similarly treated but moved to clean pasture in conjunction with the last drenching; group US was untreated and set-stocked, and group UM was left untreated but moved to clean pasture week 8 after turn-out. Supplementary feed was offered in June and August due to scarcity of pasture. Strategic treatments of ewes and lambs weeks 3, 6 and 8 after turn-out, with or without a move to clean pasture, were highly effective in controlling nematode infections for most of the season. This was reflected in better weight gains and carcass characteristics in the treated compared to untreated lambs, resulting in an average increase in the value of the product by 36%. The effect of moving without treatment (UM) on faecal egg counts was limited but peak pasture infectivity was reduced to less than 10% compared to the set-stocked group and weight gains of lambs were significantly better despite poor feed availability in late season. The study showed that under set-stocked conditions repeated anthelmintic treatments of both ewes and lambs in early season may ensure sufficient nematode control whereas moving animals to clean pasture without dosing was less efficient. The latter may, however, still be a viable option in organic and other production systems where routine use of anthelmintics is banned, particularly if weaning and moving are combined or a second move is performed.

Distribution, prevalence and intensity of Schistosoma bovis infection in cattle in Iringa district, Tanzania.

Monthly abattoir, farms and village surveys were carried out to determine the distribution, prevalence and intensity of Schistosoma bovis infection in cattle in Iringa district in the southern highlands of Tanzania between August 1991 to August 1992. Abattoir surveys were conducted at the Iringa regional abattoir and age, sex, live animal grade and livestock market of origin of each of 342 animals examined were recorded. Five grams of the central part of the jejunum were collected from each animal and schistosome egg counting was carried out after tissue digestion. Nine farms and six villages were randomly selected and age, sex and origin of 501 cattle was recorded. Faecal samples were collected from each animal and quantification of schistosome eggs was carried out by means of the Modified Bell filtration technique. Abattoir surveys revealed S. bovis to be present in 116 out of 342 cattle examined in 10 out of the 12 livestock markets surveyed giving a point prevalence of 34%. A high frequency (70.1%) of low tissue egg counts (< 200 eggs per gram) was observed among the infected animals. The prevalence and intensities of infection observed in the slaughtered cattle were not related to the age-group, sex and grade of the animals. Results from faecal egg counts in nine farms and six villages disclosed that the infection was predominant in four farms (Lulanzi, Igumbiro, Ruaha and Mlolo) and three villages (Itunundu, Ibumu and Lulanzi). Egg counts per gram of faeces (EPGF) at Lulanzi dairy farm revealed a peak egg excretion in 1-3 yr old animals which was followed by a decline in the number of EPGF within the age group of 3- to 9-yr old animals. However, the faecal egg excretion tended to rise again in animals over 9 years old. Deaths of four animals which were preceded by signs of intermittent diarrhea, loss of condition, anaemia and high faecal egg counts was observed at Lulanzi farm. Postmortem examination of the dead animals revealed that they had severe schistosomal lesions and higher tissue egg counts than the slaughtered cattle. It was concluded from the present study that S. bovis infection in cattle is very common in foci in Iringa district and possibly the whole of the southern highlands of Tanzania and in some enzootic farms it could be among the major causes of ill-health and lowered productivity.