Risks of enteropathogen infection in humans and cattle associated with manure management in urban and peri-urban areas of Morogoro, Tanzania

Abstract

Urban population growth has created an increase in demand for food including those of animal origin. In response to ample market, urban and peri-urban livestock farming has expanded both in the number of livestock and the number of households engaged in livestock keeping. As a result, human-animal interaction has increased and concurrent increase in manure production within the same land space has increased human-manure-environment contact. The present study was aimed at investigating cattle and manure management practices and associated risks of manure-borne enteropathogen infection to humans and animals and environmental contamination in urban and peri-urban settings of Morogoro, Tanzania. One hundred and nineteen smallholder dairy cattle keeping households from urban and peri-urban areas of Morogoro municipal, Morogoro rural and Mvomero districts were randomly selected for the study. To each cattle keeping household, a non-cattle keeping neighbor from within a radius of 100m was selected and a pair formed a cluster. Administration of structured questionnaires to cattle keepers and non-cattle keepers, together with observations was used to collect information about cattle and manure management practices. Individual fecal samples were collected from all cattle present at the household registered for the study. Stool samples from individuals from cattle keeping households and non-cattle keeping neighbors as well as soil and water samples were collected for the purpose of isolating zoonotic Salmonella spp., non-sorbitol fermenting diarrheagenic E. coli and non-pathogenic commensal E. coli strains. In total, there were 446 cattle fecal, 201 stool, 201 soil and 201 water samples for bacteria isolation. Zoonotic Salmonella species were isolated on Salmonella-Shigella agar and characterized by biochemical and standard serological methods. Diarrheagenic E. coli were isolated from sorbitol MacConkey agar and characterized by conventional biochemical, serological and antimicrobial susceptibility tests and molecular methods such as PCR and DNA hybridization. The non-pathogenic E. coli isolated from MacConkey agar were screened for double resistance for ampicillin and tetracycline using Petri film Select E. coli count plate and later analysed for genetic relatedness by Pulsed Field Gel Electrophoresis (PFGE). Logistic regression was used to quantify the risks for transmission of E. coli between cattle, humans, water and soil based on PFGE results. It was revealed that cattle from different herds were allowed to mix and there was indiscriminate defecation during grazing. Manure collection, conveyance and disposal resulted into direct human contact with manure and manure was disposed off within and around residential areas either as fresh or composted. The prevalence of shiga toxin-producing E. coli (STEC) O157:H7 in cattle was 0.9% (95% CI: 0.29 –237 2.15) while the prevalence of all STEC strains in cattle was 1.6% (95% CI: 0.69 – 3.08). The overall prevalence of diarrheagenic E. coli in cattle was 2.2% (95% CI: 0.99 – 3.67) and 0.5% (95% CI: 0.025 – 2.44) in water sources. This shows that cattle remain potential source of pathogenic E. coli to humans and environment. Among the non-sorbitol fermenting E. coli isolates, one Extended Spectrum Beta Lactamase (ESBL)-producing isolate showed the Multilocus Sequence Typing (MLST) type ST131 that causes antimicrobial-resistant infections in humans. Zoonotic Salmonella strains such as Salmonella amager, S. kentucky and S. weltevreden were isolated from humans and cattle. Overall, four samples out of 1046 (0.38%) were positive, while the prevalences of Salmonella in humans and cattle were 1% and 0.45% respectively. Isolation of S. amager in asymptomatic human subject shows that, the pathogen that was previously reported to cause gastroenteritis outbreak in humans, may have lost its virulence characteristics but still exists within the human population. There was transmission of E. coli between cattle, humans, soil and water within and between clusters due to manure management. Out of 44 clusters from which ampicillin and tetracycline resistant E. coli were isolated, 16 clusters (36%) had at least one isolate that was 100% identical to another isolate but from another source within the same epidemiological unit. Cattle (OR=19.2, CI: 2.04-179.8) and manure (OR=0.4, CI: 0.17-0.89) management practices were the risk factors for E. coli transmission between cattle, humans, soil and water. Cattle and manure management practices in urban and peri-urban areas of Morogoro put humans and animals at risk of infection with pathogens including E. coli O157:H7 and ESBL producing ST131 strains while contaminating the environment. Therefore, there is a need for formulation and enforcement of manure management guidelines that safeguide human, animals and the environment.