Risks Associated with Consumption of Livestock Products

The Project

The Food hygiene and consumer safety unit was established at the International Trypanotolerance Centre in 2000. It is largely funded by the German Government (Senate of Berlin) and a regional EU project (PROCORDEL). The overall objective is the assessment of public health risks, including zoonoses, derived from consumption of animal products in The Gambia and the region (Senegal, Guinea and Guinea Bissau). In consultation with the local NARS, NGO's and other organisations (e.g. National Codex Committee), relevant activities were identified and implemented. International and National Institutes (e.g. Reference Laboratories for Brucellosis and Tuberculosis), Research Institutes (e.g. Swiss Tropical Institute, CIRAD-EMVT) and Universities (e.g. FU-Berlin) are actively involved in the research work.

Background

By the year 2030, the human population of Africa will have increased threefold, necessitating a massive increase in animal production. This challenge has to be addressed in a rapidly changing context of urbanisation with greater concentration and intensified production of animals in cities and peri-urban areas. This can result in the emergence of diseases of intensification with economic consequences. The spectrum of diseases includes those posing risks to human health, such as communicable and foodborne zoonotic diseases. Tuberculosis (Tb) and brucellosis are examples of emerging or re-emerging zoonoses and contamination of milk with bacteria or zoonotic agents, leading to important and widespread foodborne diseases, are important aspects of public health. The epidemiology of these diseases is a result of complex interactions and changes in pathogens, foods, food-handling, -distribution and –consumption, and population immunity. Predicting the impact at any one point in the food chain presupposes an understanding of causes-and-effects of the whole food chain. For an assessment, the diseases have to be investigated in epidemiological field studies to determine prevalence, incidence and risk factors. Such a risk based approach responds well to demands of the worldwide new socio-economic context for the liberalisation, globalisation and harmonization of trade. Its implementation is guided by the establishment of a multilateral framework of measures, procedures, rules, regulations and standards (WTO-SPS).

Activities and first results

Work was implemented in the following areas:

• The hygienic status of milk from farms and local markets and associated potential risk for public health

In order to investigate the hygienic status of milk produced locally along the chain animal-farmer-collector-vendor, several study components were carried out (The Gambia) or are on-going (Senegal and Guinea). In Senegal, local private pasteurisation units marketing milk and milk products were also investigated. Prior to the collection of milk samples, information on milk vendors, collectors and farmers was gathered by way of structured questionnaires for the provision of information on market structures and the milk marketing chain. Preliminary results for the 3 countries demonstrate a high total level of bacteriological contamination of market milk samples. Milk is already contaminated at the producer level at high rates, this contamination is propelled to various extends along the rest of the milk commodity chain. The high proportion of Coliforms (75-100%) indicate, that contamination is most likely related to unhygienic handling along the producer-vendor chain. Bacteria with likely zoonotic and animal health importance (mastitis) were also identified (e.g. coagulase-positive Staphylococci E. coli, Listeria spp., Salmonella spp., Bacillus cereus). E. coli and Salmonella spp. are still being s ub-differentiated by Reference Laboratories for better interpretation of their zoonotic importance. The identification of contamination points along the producers-vendors chain is still on-going and will be given special consideration in follow-up studies.

• Assessment of the public health risk associated with zoonoses (Tuberculosis: Mycobacterium bovis; Cysticercosis: Cysticercus bovis; Brucellosis: Brucella abortus)

To generate necessary baseline data for the development of strategies to minimise risks of transmission of bovine tuberculosis, cysticercosis and brucellosis to humans, several pilot studies aim at providing estimates of the prevalence of these infections.

An abattoir survey (The Gambia) and on-farm screening surveys (The Gambia, Senegal, Guinea). Revealed as first results for The Gambia and Senegal that infections caused by B. abortus, M. bovis and C. bovis (The Gambia) are rare. The low prevalence rates indicate a relatively low risk for consumers related to these infections. Results from Guinea suggest a different situation for Brucellosis there. Within herd prevalence rates for B. abortus vary considerably, no reactors were found only in 8 of the 36 farms tested. Humans in the study region do consume milk raw or fermented; brucellosis obviously poses a public health risk. Cases of orchitis of men and unclear cases of 'arthritis' are first indications of infections in farming families.

Outlook

A series of follow-up studies are proposed for 2002. Risk-based evaluation methods (HACCP) will be introduced.

For more information please contact Dr Fred Unger.