Linking human health and livestock health: a “one-health” platform for integrated analysis of human health, livestock health, and economic welfare in livestock dependent communitities

Authors: THUMBI, S - Washington State University; NJENGA, KARIUKI - Centers For Disease Control - Kenya; MARSH, TOM - Washington State University; Noh, Susan; OTIANG, ELKANAH - Kenya Medical Research Institute; MUNYUA, PENINAH - Centers For Disease Control - Kenya; OCHIENG, LINUS - Kenya Medical Research Institute; OGOLA, ERIC - Kenya Medical Research Institute; YODER, JON - Washington State University; AUDI, ALLAN - Kenya Medical Research Institute; MONTGOMERY, JOEL - Centers For Disease Control - Kenya; PALMER, GUY - Washington State University; MCELWAIN, TERRY - Washington State University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2015
Publication Date: 3/23/2015
Citation: Thumbi, S.M., Njenga, K.M., Marsh, T., Noh, S.M., Otiang, E., Munyua, P., Ochieng, L., Ogola, E., Yoder, J., Audi, A., Montgomery, J., Palmer, G., Mcelwain, T. 2015. Linking human health and livestock health: a “one-health” platform for integrated analysis of human health, livestock health, and economic welfare in livestock dependent communitities. PLoS One. doi: 1371/journal.pone.0120761.

Interpretive Summary: The study platform reported in this paper is designed to investigate and understand the links between human health, animal health, and specific socio-economic variables. The key strength of this study is the simultaneous collection of longitudinal data on human and animal health, and socio-economic data from the same households. Human health and animal health may be linked through 3 main pathways: i) a socio-economic pathway where improved livestock production is associated with healthy livestock leading to improved household incomes and wealth, access to education and health care, ii) a nutritional pathway where owning healthy livestock increases access to animal source foods that in turn reduces the risk of malnutrition and disease, and iii) a zoonotic pathway where healthier livestock are less likely to transmit zoonotic and food-borne infections. Since our data are linkable at the household level, this makes it possible to identify the pathways by which human and animal health are related, determine the magnitude and direction of effect of each pathway, and test interventions in the animal sector that would increase human opportunity, including human health, wealth and welfare. This platform is designed to simultaneously investigate the incidence of 4 disease syndromes in humans and 9 disease syndromes in animals, primarily but not exclusively focusing on infectious diseases. One-year human health surveillance data shows respiratory illness (cough, pneumonia) to be the most common disease syndrome among study households, followed by febrile illnesses and gastro-intestinal illnesses in that order. For animals, gastro-intestinal illnesses were the most common disease syndrome, followed by respiratory illnesses. Although the analysis is based on only 12 months of data, we find strong associations between the cumulative number of human illnesses in a household (human sickness index) and the cumulative number of animal illnesses and death (animal sickness index) in the same households. Additionally, for the common respiratory and gastro-intestinal illnesses, households with high numbers of animal cases of each of these syndromes have high numbers of the same syndromes in humans. In the future the etiologies of these diseases will be identified and underlying factors leading to increased illness in both humans and animals within a household will be determined. It is these types of data that are sorely needed to guide disease policy and investment in resource constrained areas.

Technical Abstract: For most rural households in sub-Saharan Africa, healthy livestock play a key role in minimizing the burden associated with zoonotic diseases, and in meeting household nutritional and socio-economic needs. Although these relationships are recognized, they are complex and there is limited data on the contribution and effect size of nutritional, socio-economic, and zoonotic pathways that may link animal health to human health and welfare. To remedy this, we designed a study platform to simultaneously obtain syndromic disease data in humans and their animals from 1500 rural households in Western Kenya. Each household is visited bi-weekly and data on four human syndromes (fever, jaundice, diarrhoea and respiratory illness) and nine animal syndromes (death, respiratory, reproductive, musculoskeletal, nervous, urogenital, digestive, udder disorders, and skin disorders) are collected in cattle, sheep, goats and chickens. Additionally, a comprehensive socio-economic survey is conducted every 3 months in each household. Data collected over the first year of the study shows over 93% of the households own at least one form of livestock (55% own cattle, 88% own chickens, 41% own goats and 19% own sheep). Digestive disorders, mainly diarrheas, are the most common syndromes observed in cattle, goats and sheep, accounting for 56% of all livestock syndromes, followed by respiratory illnesses (18%). In humans, respiratory illnesses account for 54% of all cases observed, febrile illnesses 40% and gastro-intestinal tract illnesses 5%. While controlling for household size, the odds of observing a human illness case in a household increase by 1.31 times (95% CI 1.16 – 1.49) for every 10 cases of animal illness or death observed in the same household. Access and utilization of animal source foods such as milk and eggs were positively associated with the number of cattle and chickens owned by the household. Additionally, the probability of seeking health care was positively associated with household incomes and wealth, which were themselves positively associated with livestock herd size. This study provides a unique longitudinal dataset that allows for the determination and quantification of linkages between human and animal health, including the impact of healthy animals on human disease averted, malnutrition, household educational attainment, and income levels.