Key factors influencing canine heartworm, Dirofilaria immitis, in the United States

Parasites & Vectors (Impact Factor: 3.43). 10/2012; 5(1):245. DOI: 10.1186/1756-3305-5-245
Source: PubMed


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.

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Available from: Laura C Harrington, Oct 09, 2015
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    • "This fact puts dirofilariasis among the relevant parasitic Dirofilaria immitis infection in carnivores from Bulgaria: 2012–2013 update BJVM, ××, No × 2 zoonoses. The wide spreading of dirofilariae and their importance for health explains the increasing interest in their study throughout the world (Marks & Bloomfield, 1998; Schwan & Durand, 2002; Simón et al., 2005; Lee et al., 2007; Genchi et al., 2011; Brown et al., 2012; Morchón et al., 2012). "
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    ABSTRACT: Helminthological necropsies of 489 carnivores (325 golden jackals, 115 red foxes, 4 martens, 3 wolves, 27 domestic dogs and 15 cats) from Bulgaria were carried out in 2012–2013 aiming to establish infection with Dirofilaria immitis (Nematoda: Onchocercidae). The infection was found in the golden jackals, red foxes and domestic dogs. Adult worms were located in the heart (55.24%) or both in the heart and pulmonary arteries of the hosts (27.97%). Often in the place of localisation of the helminths macroscopic lesions as obturation of pulmonary arteries, thickness and granulation of the inner surface of pulmonary arteries, damaged atrioventricular valves were observed. The prevalence of infection was 37.54%, 25.22% and 33.33% in the golden jackals, red foxes and domestic dogs respectively. The infection intensity in the jackals varied between 1 and 19 specimens per animal (mean 4.1), in the foxes it was between 1 and 15 specimens (mean 4.79) and in the dogs – between 1 and 34 specimens (mean 14.43). Comparison of our data with those from literature showed a trend towards increased spread of infection in Bulgaria and South Europe in recent years. Morphometric description of D. immitis in materials from golden jackals, red foxes and domestic dogs was performed too. This is the first report in materials from golden jackals and red foxes.
    Bulgarian Journal of Veterinary Medicine 01/2015; Online first. DOI:10.15547/bjvm.918
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    • "The completion of the parasite life cycle and the transmission to dogs depends on larval development to the infective third stage (L3) in the vector. For this part of the life cycle, suitable environmental temperature is a critical factor (Genchi et al., 2009, 2011a; Brown et al., 2012). Due to global warming, average temperatures may reach a level suitable for completion of larval development of D. immitis and D. repens in the vector even in countries located in temperate zones such as Germany (Genchi et al., 2011b; Sassnau and Genchi, 2013). "
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    ABSTRACT: Recently concerns are increasing that dirofilarial nematodes may spread from endemic areas in southern, eastern and central Europe to countries in northern regions of Europe. The increasing number of autochthonous cases of canine Dirofilaria repens infections in Germany indicates that worms of this genus may invade new areas, and climate change may be a key factor in this scenario. Thus analysis of long term development of regional temperature is a pivotal factor in risk analysis related to transmission of these worms. Such information is important for suggestions of counteracting strategies, such as definition of periods of increased transmission risk and, consequently, time slots most suited for preventative measures. In this study, mean daily temperature data from 34 geographical clustered weather stations representing all parts of Germany were analyzed. It is concluded that the increasing trend for average daily temperatures observed in the period from 1984 to 2013 has led to climatic conditions that allow the completion of dirofilarial life cycles in large parts of Germany between May and October. Autochthonous infection with D. repens is already established in some regions and targeted diagnosis and medical prophylaxis is advisable for dogs assumedly exposed during risk of transmission periods. It appears likely that global warming will support further spread of D. repens. Furthermore for the population of dogs the spread of the more pathogenic species D. immitis in hitherto non-endemic Germany is a potential risk if mean temperatures rise to a level suitable for parasite development in the abundant vector mosquitoes during the warmer seasons.
    Veterinary Parasitology 09/2014; 205(1-2). DOI:10.1016/j.vetpar.2014.06.034 · 2.46 Impact Factor
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    • "The factors chosen for inclusion in this study are those envisioned to impact whether a dog is likely to have heartworm. These factors are a subset of those listed in Brown et al.[2] and contain climate variables (annual temperature, precipitation, and relative humidity; Figures 3, 4, 5); geographic factors (elevation, forest coverage, surface water coverage; Figures 6, 7, 8); societal factors (human population density and household income; Figures 9 and 10); and the presence or absence of Aedes aegypti, Aedes albopictus and six other mosquito species (Figures 11, 12, 13, 14, 15, 16, 17, 18). Presence or absence of mosquito species was used because abundance data are not available. "
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    ABSTRACT: 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.
    Parasites & Vectors 06/2014; 7(1):264. DOI:10.1186/1756-3305-7-264 · 3.43 Impact Factor
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