Prevalence of porcine cysticercosis and associated risk factors in smallholder pig production systems in Mbeya region, southern highlands of Tanzania.

Porcine cysticercosis (PC) caused by the larval stage of a zoonotic tapeworm Taenia solium, is known to pose serious economic losses and public health risk among smallholder pig production communities. The present study was conducted to determine prevalence and associated risk factors for PC in smallholder pig production systems in Mbeya region, the major pig rearing region of Tanzania. A cross-sectional survey employing a random sample of 300 pig keepers from 30 villages of Mbozi and Mbeya Rural districts, Mbeya region were used to evaluate pig production systems and practices. Concurrently, 600 male and female pigs of different age categories were randomly selected and examined for PC using lingual examination method and antigen enzyme-linked immunosorbent assay (Ag-ELISA). The overall pig level PC prevalence in Mbozi district was 11.7% (95% CI=8.5-15.8%) and 32% (95% CI: 27-37.5%) based on lingual examination and Ag-ELISA, respectively. In Mbeya Rural district, the prevalences were 6% (95% CI: 3.8-9.3%) and 30.7% (95% CI: 25.8-36.1%) by lingual examination and Ag-ELISA, respectively. In Mbozi district 46% of the households were found infected (one or more infected pigs) and the corresponding figure was 45% for Mbeya Rural district. The agreement between lingual examination and Ag-ELISA was poor (κ<0.40). There were no significant differences in the prevalence of PC in different sex categories of pigs. Significant risk factors associated with PC prevalence were free roaming of pigs (OR=2.1; 95% CI=1.3-3.6; p=0.006), past experience of porcine cysticercosis in the household (OR=2.6; 95% CI=1.5-4.8; p=0.002), increased age of pig (OR=1.9; 95% CI=1.2-3.0), slatted raised floor in pig pen (OR=8.4; 95% CI=1.0-70.0), in-house origin of the pig (OR=1.6; 95% CI=1.1-2.5) and sourcing of water from rivers (OR=3.1; 95% CI=1.6-6.3; p<0.001) and ponds (OR=5.0; 95% CI=1.2-21.7; p=0.031). This study has clearly revealed a high sero-prevalence of PC in the study area, which imposes a major economical and public health burden to the smallholder pig farmers. The study also points to a number of important risk factors in smallholder pig management that may be addressed (e.g. confinement, quality of pens and water sources) in future interventions and educational campaigns for control of T. solium.

Improving pig husbandry in tropical resource-poor communities and its potential to reduce risk of porcine cysticercosis.

To minimise the risk of cysticercosis in pigs it is necessary to raise pigs in confinement. The prevailing production system using free-range pigs is apparently very resilient although economic studies have shown that these traditional production systems are wasteful and unprofitable due to poor feed conversion, high mortality rates, low reproductive rates and poor final products. However, experiences from Africa show that intensive pig farming is stagnant and the sustainability of the traditional sector is better than that of the intensive sector. Examples from various African countries are given on the failure of intensive pig farming. This apparent paradox has various explanations. The lower fixed cost of traditional pig production compared with intensive production is one. Another explanation is that many households have some kind of kitchen waste, which can be exploited by a pig, but there is only enough for the partial feeding of a single pig. A third explanation of the paradox is that the pig has functions that are not reflected in a simple economic balance. The pig is a source of capital income, which can be realised at times of major expenses, and it can also be used as a way to put aside small amounts of money, which alternatively might evaporate. The pig's scavenging behaviour has clear nutritional benefits. Thus, a diet consisting of e.g. maize or sorghum, which are some of the feeds available on the small farms, will only provide approximately 30% of the pigs requirements of lysine and methionine, which are the most limiting amino-acids in pig feeds. Simulations with data available for green feeds and material of animal origin show that a 20% "supplement" from the fields may increase the amino-acid provision to about 80% of the optimum. If pigs are kept enclosed this supplement has to be fed to the pig which involves purchase and labour costs. The paper discusses the various options in terms of feeding, housing and use of genetic resources for the improvement of pig husbandry in tropical resource-poor countries.