We use cookies on our website. Some are necessary for the operation of the website. You can also allow cookies for statistical purposes. You can adjust the data protection settings or agree to all cookies directly.
Data Protection Declaration
Imprint
SFB 564: D4.1 - Livestock parasites and parasitic zoonoses in smallholder farming systems of Northern Vietnam
Project
Project code: DFG SFB 564: D4.1
Contract period: 01.07.2003
- 30.06.2006
Purpose of research: Applied research
80% of the Vietnamese population inhabits rural areas, which are dominated by agriculture. After rice production, animal husbandry is the 2nd most important agricultural activity. In the mountainous area of northwestern Vietnam, livestock production is mainly done in smallholder farms, with each farmer keeping small numbers of a variety of species including pigs, cattle, buffaloes, goats and poultry. Within this area dominated by economic constraints, smallholder farming differs according to the distance to towns where market outlets exist. While farmers in valleys (near roads or towns) use e.g. pig production for income generation, the more remote mountain slopes are dominated by subsistence farming. In adaptation to this, different husbandry practices exist, and different animal species / breeds are raised. Generally, pigs are the most important animal species both as a meat source and for sale.
While local pig genotypes are gradually being replaced by high yielding exotic breeds in large areas of Vietnam, this development is only slowly reaching the more remote areas of the northwest. Presently, aspects of resource utilization with regard to different animal breeds are under investigation (cf. sub-project D2.2 (Livestock effiency)). However, the impact of this development on aspects of veterinary and public health importance have not been addressed so far, although the transmission of economically important livestock pathogens and zoonotic diseases are intricately linked to husbandry practices and animal genotypes.
Several species of livestock parasites not only have economic importance due to their impact on the quality and quantity of animal products, but are causative agents for human disease. Due to the complex life cycles of most parasites – which involve different host species and obligatory host changes – the locally prevailing conditions of animal husbandry, slaughtering facilities and marketing practises have a drastic influence on the transmission intensity. Many parasitic diseases can be effectively controlled by improved slaughtering practises (meat inspection) and information on preventive behaviour to farmers and distributors. However, small scale farming usually favours disease transmission due to uncontrolled home slaughter with unsafe offal disposal and generally unhygienic conditions. Therefore, any changes in animal production systems and the introduction of new animal genotypes is likely to have an impact on parasite transmission and public health, which has to be taken into account when evaluating the local acceptance and sustainability of such systems.
In a first phase of this project, prevalence surveys of various parasite species in livestock (pigs, cattle, buffaloes, goats) will be carried out in an area of Son La Province, which includes different types of animal husbandry. Several species of parasites with economic or public health importance are known to occur in the area and will be surveyed (using appropriate epidemiological methods) according to livestock species and area of origin. The parasite range to be addressed will include:
Sarcocystis spp. are non-zoonotic protozoan parasites, which cause cystic stages in muscle tissue of e.g. pigs,cattle and goats. Meat quality is reduced, growth is impaired and heavily infected animals may die. Different species of Sarcocystis are likely to occur in the area, which are specifically transmitted to livestock by different species of carnivores (e.g. dogs and cats), and by man. Unidentified species of Sarcocystis are frequent parasites of livestock in the area.
Taenia solium is a tapeworm of man which involves the pig in its cyclic transmission. The cystic stages in pig muscles (cysticerci) reduce meat quality, but the main importance is its role as causative agent of human neurocysticercosis, a serious and often lethal disease affecting the central nervous system (brain, eyes). On a world scale, the parasite’s presence is strongly associated with small-scale pig breeding, and it is known to occur in the area.
Echinococcus spp. are tapeworm species transmitted by canids (usually dogs) to different species of livestock and to man. While different genotypes of E. granulosus mainly use pigs and goats for transmission, E. ortleppi is a parasite of cattle. In livestock and man the parasites cause hydatidosis, characterized by large fluid filled cysts developing in internal organs, mainly liver and lungs. In animals the parasite leads to impaired growth and at slaughter causes the condemnation of internal organs, while in man untreated hydatidosis is often fatal. Pathogenicity to man is strongly associated with species and genotype of the parasite. While the presence of Echinococcus is known from northern Vietnam, no information exists on genotypes and prevalence rates.
Trichinella spp. are nematode tissue parasites affecting carnivorous or omnivorous warm-blooded animals including man. The parasites are acquired by eating insufficiently cooked meat from infected animals (mainly pork). Acute infections with heavy doses can lead to death within a few days. Serious human infections often occur as outbreaks which can be traced to a common source, but sub-lethal infections are widespread in endemic areas where the cause of disease often remains unidentified. In Vietnam, the parasite is known to be widespread and to occur locally at high prevalence levels in pigs and dogs. Several outbreaks of human trichinellosis are on record.
The survey involves identification of the parasite to species and – where necessary - to genotype levels, and GIS-based documentation. Different diagnostic techniques will be developed and/or evaluated for their applicability under local conditions. Where appropriate (e.g. with pigs) the susceptibility of different animal genotypes will be estimated. Based on the survey results, the parasite species for further epidemiological study on farm level will be selected.
In a second project phase, transmission of selected parasite species will be studied on ca. 100 farms of different economic levels, which are also participating in sub-project D2.2 (Livestock efficiency). This study includes the examination of slaughtered animals which had been raised on the respective farm (pig, cattle, buffalo, goat), using parasitological and molecular methods. Depending on the parasite species to be addressed, faecal samples of possible transmitters (dogs, cats, humans) will be tested, and other species which may be involved in the life cycle (e.g. rodents with Trichinella) will be examined. In addition, information on risk behaviour will be obtained by questionnaires and interviews of the farmer and other relevant parts of the population (e.g. butchers, medical and veterinary personnel).
Finally, transmission routes of exemplary parasites will be evaluated according to a variety of parameters (including animal genotypes, husbandry conditions and environmental situations), and the information obtained will be used to devise preventive strategies (both at farm level and in the public health domain), which are appropriate and feasible under the local conditions. Blocking the transmission routes of parasites will finally result in increased productibility and quality of livestock and may have an impact on the market potential of livestock and their products. Therefore, D4.1 is also linked with the sub-project E3.2 (Product marketing) which analyzes the market potential of agricultural products. The data generated in this project will also provide valuable information for future use in quality control systems for small-scale meat production and therefore enhance the competitiveness of farmers in remote areas on the national and international meat market.
Section overview
Subjects
- Animal health
