Date of Award

January 2016

Document Type

Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Albert Ko

Abstract

Leptospirosis is a neglected zoonotic disease with a worldwide distribution, yet disproportionally affects poor rural subsistence farmers in the tropics. The animal reservoirs for spill-over infection to humans in such settings in the South Pacific have not been well delineated, thus hampering effective control efforts. We conducted a case control investigation among households that participated in a seroprevalence survey for leptospirosis in Western Fiji. We surveyed domestic animals and trapped rodents at 45 cases and 73 control households who had one or more, and no inhabitants with evidence for anti-leptospire agglutinating antibodies. We performed serology among all animals and used polymerase chain reaction to detect Leptospira DNA in kidneys of trapped rodents. One or more seropositive animals were identified among 78% of the 96 households with domestic animals or trapped rodents. There was not a significant difference between the presence of seropositive animals between case and control household (67% vs 85%, respectively). Agglutinating antibodies were detected from a high proportion of households with horses (85%) and cattle (73%), indicating that the seroprevalence of leptospirosis in livestock was high in this region. Agglutinating antibodies against serogroup Australis, which was recognized by 64% of the seropositive human inhabitants, were detected from six of the seven animal species. Additionally, a proportional similarity index analysis indicated that cattle, horses, dogs, rodents and humans form a transmission network. There was a non-significant trend for Leptospira DNA positive rats to be trapped in case vs control households (OR 5.71, p=0.09). Our studying findings indicate that there exists a complex network of transmission between livestock, domestic animals and rodents in Western Fiji, and the source for human leptospirosis cannot be attributed to a single reservoir species. Therefore, control of leptospirosis in rural Fiji and similar high transmission settings will need to rely on multiple intersectorial strategies that target prevention of leptospirosis in livestock, rodent control, the use of personal protection and barrier approaches, and reduction of high risk behaviors.

Comments

This thesis is restricted to Yale network users only. It will be made publicly available on 12/19/2018

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