Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 92-98).

No description available.

The four objectives of this study were to determine: 1) the incidence of Dirofilaria immitis and Dipetalonema reconditum in dogs of East Central Indiana, 2) the variables significantly affecting the incidence of each parasite, 3) the correlation of heartworm infections with clinical symptoms, and 4) to determine whether Dirofilaria immitis and Dipetalonema reconditum are endemic in Indiana.From December, 1973 to April, 1974, blood samples were taken from 335 dogs in East Central Indiana and were examined for microfilariae using the direct smear and the modified Knott concentration techniques. At the same time, complete information on each dog was collected on a "SURVEY INFORMATION” form. The data was statistically analyzed by crosstabulation of each variable with the results of the blood tests for each parasite. Levels of significance were computed using chi square values with appropriate degrees of freedom. Values of 0.05 were considered to be significant.In this study, the overall incidence of Dirofilaria immitis was found to be 3°% which included one dog infected with both parasites. Of the 131 hunting dogs, 6.1% were infected, while only 1% of the 204 non-hunting dogs were infected. Furthermore, all of the dogs infected with heart-worms were those which were principally outdoor dogs. These differences were significant and they reflect thehigher exposure risk of hunting dogs and dogs living out-doors to the mosquito vectors.The incidence of Dipetalonema reconditum was 6% overall with 11.5 % of the hunting dogs and 2.5% of the non-hunting dogs infected. It was most prevalent in dogs three to six years of age. After age seven the prevalence declined sharply. This decrease with age may be the result of an immune response to the infective larvae which prevents reinfection.Clinical symptoms could not be correlated with infections with Dirofilaria immitis since 90% of the dogs infected with heartworms had no symptoms of the disease. This indicates that most of the heartworm infections in dogs of this area are light, probably involving few adult worms. The results of this study indicate that Dirofilaria imnitis and Dipetalonema reconditum are endemic in Indiana, as 60% of the dogs with heart-worms and 35% of the dogs with Dipetalonema reconditum had never been out of the state.

Canine immunoglobulins of the IgG group were shown to be intimately associated with the cuticle of circulating non-infection Dirofilaria immitis microfilaria. The significance of these immunoglobulins in blocking a complete immune response in the definitive host is discussed. Immunodiffusion, immunoelectrophoresis and fluorescent inhibition techniques are described and their applicability to the study of host-parasite relationships are evaluated. A rapid reproducible method for the production of specifically labeled anti-D. immitis microfilaria globulins is presented.

Microfilarial enhancement of viral transmission is well documented, however only one previously studied model used components that occur together in nature and therefore has realistic implications. La Crosse (LAC) virus encephalitis is the most common mosquito-borne illness affecting children in the United States. LAC virus is prevalent in the Great Lake and Mid-Atlantic states and coincidently this area overlaps the region of highest infection for Dirofilaria immitis, the nematode that cause canine heartworm disease. Ae. albopictus and Oc. triseriatus are important vectors of La Crosse virus and among the numerous species able to transmit D. immitis. In this study, Aedes albopictus and Ochlerotatus triseriatus were infected with La Crosse virus and Dirofilaria immitis to determine the effects of dual infection on the dissemination and transmission of the virus. The effects of dual infection varied between the species tested. Ae. albopictus had significantly higher tolerance to D. immitis infection than Oc. triseriatus. Dissemination for dually infected Ae. albopictus were higher than the control group for all days tested, except one. Transmission rates for D. immitis infected Ae. albopictus were significantly higher than the control group on day 14 post infection. No microfilarial enhancement of viral dissemination or transmission was observed for Oc. triseriatus. The infection, dissemination, and tranmission rates were low for both species compared to rates of previous studies. Low rates could be a result of low susceptibility for the strains tested. In a second study, mosquitoes were collected from two counties in Southwestern Virginia to determine the abundance of potential La Crosse virus and D. immitis vector species. The abundance and distribution of mosquito species were examined in 2003 and 2004 using gravid traps. An unexpected finding was the significant increase in the abundance of Ochlerotatus japonicus. In 2003, collections were made over 192 trap nights from June to August yielding 5,879 mosquitoes of which only 24 were Oc. japonicus. In 2004, 12,151 mosquitoes were trapped from June to September over 160 trap nights. Oc. japonicus was the second most abundant mosquito species and the dominant Ochlerotatus species collected in gravid traps. Oc. japonicus was collected in low numbers in June, but the abundance increased significantly in July and remained consistent throughout the rest of the season. Of the other major mosquito species collected in this study, only Aedes albopictus exhibited a similar seasonal pattern as Oc. japonicus. Other biological similarities of Oc. japonicus and Ae. albopictus are discussed. / Master of Science in Life Sciences

An examination of the Companion Animal Parasite Council's (CAPC) canine heartworm data to clarify the spatial prevalence of heartworm in the United States. Factors thought to influence the spatial risk of disease, as identified in a recent CAPC workshop, are discussed.

Thesis (Ph. D.)--University of Florida, 1980. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 157-167).

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 113-137).

This study was carried out to determine the usefulness of standard electrocardiography for the diagnosis of early canine heartworm disease. Baseline electrocardiograms were recorded in 12 dogs. Thirty artificial Dirofilaria immitis worms were inserted in the pulmonary artery of each dog. New electrocardiograms were recorded on days 1-4, 7, 14, 21, 28 and 35 after insertion of worms. A significant attenuation of amplitude of Q wave in lead I was recorded on days 1-4, 7, 14, 21, 28 and 35; of R wave in lead II on days 21, 28 and 35; and of S wave in lead aVR on days 7, 14, 21, 28 and 35. Duration of the QRS complex in lead AVF was significantly prolonged on day 14. In 41.6% of the dogs, right axis deviation was recorded. These results suggest that for a dog whose normal baseline standard electrocardiogram is known, a comparison of the QRS complex of the baseline with those of subsequent standard electrocardiograms may suggest early canine heartworm disease when there is an attenuation of amplitude of Q wave in lead I, R wave in lead II and S wave in lead aVR. An additional indication can be right axis deviation.

BACKGROUND:This paper examines the individual factors that influence prevalence rates of canine heartworm in the contiguous United States. A data set provided by the Companion Animal Parasite Council, which contains county-by-county results of over nine million heartworm tests conducted during 2011 and 2012, is analyzed for predictive structure. The goal is to identify the factors that are important in predicting high canine heartworm prevalence rates.METHODS:The factors considered in this study are those envisioned to impact whether a dog is likely to have heartworm. The factors include climate conditions (annual temperature, precipitation, and relative humidity), socio-economic conditions (population density, household income), local topography (surface water and forestation coverage, elevation), and vector presence (several mosquito species). A baseline heartworm prevalence map is constructed using estimated proportions of positive tests in each county of the United States. A smoothing algorithm is employed to remove localized small-scale variation and highlight large-scale structures of the prevalence rates. Logistic regression is used to identify significant factors for predicting heartworm prevalence.RESULTS:All of the examined factors have power in predicting heartworm prevalence, including median household income, annual temperature, county elevation, and presence of the mosquitoes Aedes trivittatus, Aedes sierrensis and Culex quinquefasciatus. Interactions among factors also exist.CONCLUSIONS:The factors identified are significant in predicting heartworm prevalence. The factor list is likely incomplete due to data deficiencies. For example, coyotes and feral dogs are known reservoirs of heartworm infection. Unfortunately, no complete data of their populations were available. The regression model considered is currently being explored to forecast future values of heartworm prevalence.