Document Type

MS Thesis

Publication Date



Canine heartworm (Dirofilaria immitis), is a nematode parasite that infects canines, both wild and domestic and other vertebrate hosts like ferrets, otters, and cats worldwide. The disease, dirofilariasis, can be fatal in advanced stages if untreated and is recognized as a significant concern in veterinary medicine. Canine heartworm has been reported in 49 states of the United States (U.S.) and is considered enzootic. The nematode lifecycle is dependent upon canines infected with adult worms that produce microfilaria, the vermiform embryonic stage, that circulate in the peripheral blood of the host and the mosquito vectors that ingest them taking a blood meal from the infected canine. The three-fold objective of this research was to (1) conduct a biological survey and inventory of the mosquito population in the Cumberland Gap Region (CGR) of southern Appalachia; (2) determine the mosquito species infected with Dirofilaria immitis larvae; (3) estimate the prevalence of D. immitis in the mosquito population for its transmission to pet dogs in communities within the CGR. Adult female questing and gravid mosquitos (n=2455) (representing 778 pools) were collected each year from May to September during 2017, 2018, and 2019 in an area encompassing the campus of Lincoln Memorial University in Harrogate, TN focused in Claiborne county. This was accomplished using CO2 baited CDC gravid and questing traps. Three collection zones were the focus of this research. Collection area A had high residential density, with ~42 homes per km2. It had sparse forest cover and a relatively high number of free-roaming dogs observed during the study. Collection area B had moderate residential density, with ~13 homes per km2 with dense forest cover and frequent free-roaming dogs were observed during the study. Collection area C had the lowest residential density, with ~7 homes per km2 with a mix of dense forest cover proximal to a local dog park. This location has transient dog visitation and no free-roaming dogs were noted during the study. Collected mosquitoes were euthanized by freezing overnight at -20°C and sorted into pools by species based on collection site and date. There were 2455 collected specimens representing 5 main species: Culex pipiens (n=521, pools=175), Aedes albopictus (n=460, pools=138), Aedes japonicus (n=417, pools=111), Anopheles punctipennis (n=186, pools=74) and Aedes vexans (n=172, pools=62). Another species significant to this study but found less frequently was Anopheles quadrimaculatus (n=13, pools=7). Culex pipiens was the most prevalent mosquito species accounting for 24.05% of the species collected overall. Pools of sorted mosquitoes were assayed via PCR to detect the presence of D. immitis DNA. Five (0.57%) of 778 assayed pools were positive. The positive pooled species identified were: An. quadrimaculatus (2 pools), Ae. albopictus, Ae japonicus, and Ae. vexans. All these species are recognized as established vectors of CHW in Tennessee. The identification of Ae. japonicus in this study is the 1st report of its vector potential for transmission of CHW in Eastern Tennessee.


This thesis is submitted to LMU Institutional Repository by Dr. Charles Faulkner (Major Professor) on behalf of Ms Michelle Norden (6/25/2024).