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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Vector Competence of Northern California Mosquitoes for Dirofilaria immitis (Spirurida: Onchocercidae)

Dian, Rebekah Lynn 01 January 2018 (has links) (PDF)
Dirofilaria immitis, commonly known as dog heartworm, is a dangerous filarial nematode that is transmitted by a mosquito vector. Although this parasite is historically localized to regions closer to the equator, the last few decades have experienced an increase in the amount of dog heartworm cases in Northern California, most notably in Lake and San Joaquin Counties. The primary vector of D. immitis in Northern California is Aedes sierrensis, but it is not prevalent enough in some counties to explain the increase in infections. Because of this, more prevalent and abundant species should be assessed for their ability to transmit heartworm. Culex pipiens complex (wild) and Culiseta incidens (laboratory-raised colonies) were chosen as potential vectors during this study due to their ability to meet several key vector criteria, their relative abundance in the areas of interest, and the fact that they habitually take bloodmeals from domestic dogs. Additionally, Ae. sierrensis colonies were used in this study, based on previous knowledge that they are highly competent vectors. Female mosquitoes were infected with 2.5, 5, or 10 mff/ul of D. immitis-infected blood, and decapitated at 15, 18, and 21 days post-infection. Mosquitoes were subsequently tested via qPCR for the presence and relative quantification of D. immitis DNA. We found that Ae. sierrensis and Cx. pipiens complex were both able to support the development of D. immitis to its infective stage, while Cs. incidens was not a competent vector. We also concluded that including a standard curve of known amounts of D. immitis larvae makes it possible to approximate the intensity of the infection in the mosquito. The identification of these important vectors, and the ability to assess infection intensity, may be helpful in the continued vector control efforts in Northern California and beyond.
2

Vector Competence of Aedes sierrensis and Culex pipiens complex (Diptera: Culicidae) for Dirofilaria immitis (Spirurida: Onchocercidae) in Northern California

Kurosaka, Jeffrey Allan 01 January 2017 (has links) (PDF)
Dirofilaria immitis Leidy (dog heartworm) is a life-threatening parasite transmitted by mosquitoes to domestic dogs. Endemic in the eastern United States, cases have become more prevalent over the last few decades. While prevalence in California is generally low, Lake and San Joaquin Counties have reported rates comparable to the East Coast at 3.73% and 0.71%(CAPC 2017), respectively. Aedes sierrensis is thought to be responsible for transmission in California, but in some cases, it exists in inadequate quantities and temporal ranges to explain parasite activity. Based on Huang et al. (2013) and Tran (2016), bloodfeeding patterns, and other vector criteria, Culex pipiens complex and Culiseta incidens were chosen to evaluate for vector competence. Female field-caught mosquitoes were reared, infected (2.5-5 mff/μl), and decapitated at 15, 18, or 21 days post infection (dpi). Cs. incidens was reluctant to feed using an artificial feeding system and will require additional trials. On the contrary, trials on Ae. sierrensis and Cx. pipiens complex were both completed successfully. Both species were determined to be competent vectors of D. immitis. Based on our findings, more than half of Ae. sierrensis females produced emerging L3s by 21 dpi, while Cx. pipiens complex never produced L3s in more than 5% of females. In conjunction with other factors such as the detection of D. immitis in wild mosquitoes, host-seeking preferences for domestic dogs, and appropriate temporal overlap, this suggests that both Ae. sierrensis and Cx. pipiens complex may play central roles in Lake or San Joaquin Counties, CA when abundant. Targeted control efforts are necessary to reduce the incidence of canine heartworm in these areas. While Lake and San Joaquin Counties, CA were the focus of this study, our results may be applicable to the western United States when these species are relevant.

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