Food safety interventions in periurban dairy farming systems in West Africa

Lead Research Organisation: Royal Veterinary College
Department Name: Production and Population Health


Periurban dairy farming is an expanding livestock system in West Africa where it contributes to food security and dietary diversity by supplying milk and dairy products to rapidly growing urban populations. However, periurban dairy farms are also a source of milk-borne zoonotic pathogens. In a context of scarce resources, it is critical that specific pathogens are prioritized and risk mitigation strategies selected on the basis of the likely public health benefits of their adoption. Furthermore, strategies must be acceptable by livestock keepers and consumers. In this project, epidemiological field studies will be conducted to estimate the frequency of and identify farm-level risk factors for selected milk-borne pathogens in some of the main periurban dairy production zones of West Africa. Probabilistic risk assessment will be used to quantify the impact of implementing specific risk mitigation strategies at pre-harvest, harvest and postharvest level on the probability of human exposure. The results from two parallel studies, one evaluating knowledge, attitudes and practices of periurban dairy farmers with regard to brucellosis, the second assessing the economic impact of brucellosis for this group of farmers, will inform this project to ensure that tested interventions are feasible and acceptable. This PhD studentship is linked to a project funded by the ZELS initiative and it will align with others in the ZELS Associated Studentships (ZELS-AS) programme through common interests in developing interdisciplinary approaches to tackle zoonotic diseases. The project will involve key stakeholders currently working on the safety of food of animal origin in West Africa to ensure maximum policy impact. Study results will be incorporated into capacity building activities planned as part of the ZELS project within which this PhD project will take place.

Studentship Projects

Project Reference Relationship Related To Start End Student Name
BB/N503563/1 30/09/2015 29/09/2019
1689843 Studentship BB/N503563/1 26/01/2016 24/07/2019 Bhagyalakshmi Chengat Prakashbabu
Description So far two major components of the project have been finished.1. Cross-sectional study- The data from the cross-sectional study was analysed using multiple correspondence analysis and hierarchical cluster analysis. This revealed three different typologies of dairy farms: 1) small herds with other species of animals (sheep, goat, and poultry) kept in the backyard and sells milk locally, 2) larger transhumant, mostly cattle only herds, 3) medium sized herds kept indoor with better biosecurity measures. The thematic analysis of data from focus groups showed that milk is a culturally important food and forms part of different meals of the day. Priority is given to older people and young children followed by pregnant women, head of the household and other adults when the milk is rationed. Women who run organised mini processing units boil milk before processing and are aware of milk-borne diseases. However, unorganised milk processors never boil milk. There was a lack of knowledge regarding transmission of diseases through milk among both dairy farmers and unorganised milk processors. Interestingly irrelevant associations such milk consumption and occurrence of malaria was mentioned in several discussion suggesting public health communication needs improvement.
The bulk milk samples collected were analysed using quantitative PCR to detect and quantify Staphylococcus aureus, Coxiella burnetti, Listeria monocytogenes, Salmonella spp, Escherichia coli O157:H7, Mycobacterium tuberculosis complex (MTBC), Mycobacterium bovis and Campylobacter jejuni.
A total of 248 samples were collected and analysed. Among the pathogens analysed, the most common was Staphylococcus aureus, 48.4% of the samples positive with 140-13x104 genome copies per ml of milk. Coxiella burnetti DNA was also detected in a significant proportion of samples (22.2%). Listeria monocytogenes (2.5%, 20-40 genome copies/ml), Salmonella spp (2%, 50-132 genome copies/ml), Escherichia coli O157:H7 (2% 2-180 genome copies/ml), Mycobacterium tuberculosis complex (MTBC) (2%, 35-502 genome copies/ml) and Campylobacter jejuni (1.7% 230-890 genome copies/ml) were also detected. M bovis could not be identified in any. The results suggest that there is a considerable proportion of bulk milk samples are contaminated with pathogens that are harmful to human health. Disease control strategies should be deployed along the milk supply chain to ensure public health safety as raw milk consumption is very common in Senegal.
A quantitative risk assessment was conducted to estimate the risks of illness due to Staphylococcus aureus, Listeria monocytogenes, Salmonella spp, and Escherichia coli O157:H7 among consumers of raw milk and fermented milk. it was found that traditional fermentation mitigates the risks of all the bacteria due to increase in acidity except for S. aureus. E. coli O157:H7 was estimated to cause a higher number of cases. Among the intervention simulated a chilled distribution system was found to significantly reduce the number of cases.
Exploitation Route The farm characteristics identified and the information on processing practices will be used to inform the probabilistic risk assessment, which will be done in the next stages of this project. The findings will be shared with local stakeholders, which will increase the awareness about the risks of milk-borne infections and how to mitigate them.

This is a first large-scale study that looked at important milk-borne hazards in bulk milk samples from three different regions in Senegal. The data generated gives the baseline information on the quality of bulk milk samples. This information can be utilised by policymakers to design control strategies targetted at specific pathogens. In addition, it can be further put to use by researchers to conduct risk assessments to quantify the risks to milk and milk product consumers.
Sectors Agriculture, Food and Drink

Description Findings from the study have been shared with IRD. It provided them with an idea of potential zoonosis risk in their target population and which groups are more vulnerable. I believe it will help them in targeting groups while implementing further projects in the future . Furthermore, there has been two-way interactions between the researcher and dairy farmers and milk processors during focus group discussions. During this, the participants asked questions related to zoonoses and how to control them. This was explained to the participants. This increased their awareness about zoonoses, how they are transmitted and will help them in better farm management to control zoonoses.
Sector Agriculture, Food and Drink
Impact Types Societal

Description The Association for Veterinary Teaching and Research Work Bursary
Amount £250 (GBP)
Organisation Association for Veterinary Teaching and Research Work 
Sector Charity/Non Profit
Country United Kingdom
Start 08/2018 
End 09/2018
Title Quantitative microbial risk assessment models 
Description Models to estimate the risk of illness to consumers of raw and fermented milk from selected milk borne pathogens are developed. 
Type Of Material Computer model/algorithm 
Year Produced 2019 
Provided To Others? No  
Impact The outcomes from the models suggest that consumers of raw milk purchased from milk collectors who sell milk in the markets without any chilling facilities are at higher risk of illness. Fermentation of milk may protect consumers from some pathogens however some pathogens can still grow at low pH increases the risk to consumers of fermented milk. The outcomes highlight the riskiest route through which milk and milk products reach consumers which can targetted for future interventions. In addition, chilling was found to be effective at reducing the number of estimated cases of illnesses suggesting a potential intervention. 
Title cross-sectional database of dairy farms 
Description The database consists of data on farm characteristics, milk hygiene, milking practices and consumption practices. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact The database will provide baseline data on farm characteristics and several risk factors for different zoonotic diseases. Later, this database will be populated with results of bulk milk sample testing. The bulk milk collected will be tested for selected milk-borne pathogens. This database can be used to better understand the system, identify target groups for diseases control and resource allocation. 
Description Collaboration with Animal and Plant Health Agency 
Organisation Animal and Plant Health Agency
Department Plant Health and Seeds Inspectorate (PHSI)
Country United Kingdom 
Sector Public 
PI Contribution All the collaborators were given co-authorship in the publications arisen from this collaboration.
Collaborator Contribution The bulk milk samples collected as part of the study were received by APHA who extracted the DNA for further analysis.
Impact The dataset with the prevalence of selected milk-borne pathogens in bulk milk samples from Senegal, which provides crucial baseline information is the direct result of this collaboration.
Start Year 2016
Description Collaboration with Ecole Inter États Sciences Et De Médecine Vétérinaires De Dakar (EISMV) 
Organisation Inter State School of Veterinary Sciences and Medicine of Dakar
Country Senegal 
Sector Academic/University 
PI Contribution A workshop was organised as part of project BB/L019078/1 in December 2017. during this workshop, I gave training to participants of the workshop and Public health masters students at EISMV on Data collection software (Open Data kit - ODK).
Collaborator Contribution EISMV helped me in organising the fieldwork by sharing contacts of veterinarians and animal health workers who assisted in the recruitment of the farmers.
Impact 1. Cross-sectional study in Dakar and Thies- A cross-sectional study to gather data on milk hygiene practices, milk and milk product consumption was conducted. The farm selection and recruitment were done through the collaboration with EISMV. 2. A small consumer study was conducted to understand milk and milk products consumption pattern among urban consumers which was conducted in collaboration with EISMV
Start Year 2016
Description Collaboration with Edinburgh Napier University 
Organisation Edinburgh Napier University
Country United Kingdom 
Sector Academic/University 
PI Contribution All the collaborators were given co-authorship in the publications arisen from the collaboration
Collaborator Contribution The laboratory analysis of DNA from the bulk milk samples collected from Senegal to detect milk-borne pathogens was conducted at Edinburgh Napier University. Their laboratory resources were used by the Ph.D. student. The student also received supervision while conducting lab analysis.
Impact The main output from the collaboration is the database with the presence and level of pathogens identified in bulk milk samples collected from Senegal.
Start Year 2018
Description Collaboration with Institut de recherche pour le développement (IRD) 
Organisation Research Institute for Development
Country New Caledonia 
Sector Academic/University 
PI Contribution IRD is a research institute with a research center located in Fatick (one of the study regions of the project). They have been conducting projects aimed at improving human health in the region for the past 30 years. All the preliminary findings from the study have been shared with IRD. This will help them to better understand the target population in terms of dairy farming, milk and milk product consumption. This will help them to recognize the risk of potential milk-borne hazards and prioritise their resources accordingly. This will hopefully assist them in achieving their aims of improving human health in the region.
Collaborator Contribution IRD had a list of households with details of number and type of animals kept. This allowed us to randomly select 110 households with dairy cattle for the cross-sectional study. Furthermore, they also assisted in recruiting participants for the focus group discussions with dairy farmers and women milk processors. As IRD has been working in the region for 30 years, it was easy to build trust and the participants opened up quickly during the discussions.
Impact 1. Cross-sectional study in Fatick- The aim of the study was to gather data on farm characteristics, milking hygiene and milk and milk product cosumption.2.Focus group discussions.- The aim was to understand knowledge, awareness and practices related to milk-borne diseases.
Start Year 2016