Date of Award

Spring 2023

Document Type

Honors Thesis


Basic Biomedical Science

First Advisor

Dr. Jose Pietri

Second Advisor

Dr. Daniel Bird

Third Advisor

Dr. Victor Huber


Cockroach, Salmonella typhimurium, Horizontal Transmission


Cockroaches, including the German cockroach (Blattella germanica), are common urban pests that have been linked epidemiologically and experimentally to the transmission of bacteria that cause enteric disease in humans and animals, such as the widespread pathogen Salmonella enterica serovar Typhimurium. While recent strides have been made in understanding the mechanisms and dynamics of Salmonella infection of the cockroach gut, much about this vector-pathogen relationship remains unknown. A particular knowledge gap is understanding the ecology of how S. Typhimurium is acquired, maintained, and spread by cockroaches. The behavioral ecology of German cockroaches is unique among insect vectors. They closely share shelter and food and water and consume each other’s feces, vomit, and corpses. Given these properties, we hypothesized that S. Typhimurium may be horizontally transmitted among German cockroaches by one or more routes, which could potentially enhance vector-borne transmission to humans and other animals. Here, we investigated whether horizontal transmission of S. Typhimurium occurs in B. germanica as well as its mechanisms. We examined the ability of uninfected cockroaches to become infected when co-housed with infected cockroaches under several conditions. We also investigated whether shared food and water sources, or consumption of cockroach feces or dead infected bodies, could serve as routes of horizontal transmission. Our data demonstrate that true horizontal transmission of S. Typhimurium occurs among B. germanica. That is, uninfected cockroaches acquire infection of the gut when co-housed with other orally infected cockroaches, albeit at low frequency. Further, we provide definitive evidence that consumption of feces (coprophagy) and cannibalism of dead insects (necrophagy) are routes of transmission but could not exclude sharing of food or water as contributing routes.



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