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We evaluated degree-day predictions of Dirofilaria immitis development (HDU) under constant and fluctuating temperature treatments of equal average daily temperature. Aedes aegypti mosquitoes were infected with D. immitis microfilariae and parasite development was recorded at set time points in dissected mosquitoes. Time to L3 development in Malpighian tubules and detection in mosquito heads was shorter for larvae experiencing a daily regime of 19±9°C than larvae at constant 19°C; larval development rate in Malpighian tubules was slower in fluctuating regimes maintained above the 14°C developmental threshold than larvae under constant temperatures. We showed that hourly temperature modeling more accurately predicted D. immitis development to infective L3 stage. Development time differed between fluctuating and constant temperature treatments spanning the 14°C development threshold, implicating a physiological basis for these discrepancies. We conclude that average daily temperature models underestimate L3 development—and consequently dog heartworm transmission risk—at colder temperatures, and spatio-temporal models of D. immitis transmission risk should use hourly temperature data when analyzing high daily temperature ranges spanning 14°C.

OBJECTIVE To assess knowledge, attitudes, and practices regarding heartworms (Dirofilaria immitis) and mosquito vectors among residents (dog owners and non-dog owners) in 2 neighborhoods in Florida and to perform entomological surveys of mosquito species in these neighborhoods and identify mosquito species infected with heartworm. DESIGN Cross-sectional study. SAMPLE 2,572 mosquitoes and 96 residents of 2 northern Florida communities. PROCEDURES A 32-item questionnaire was orally administered to a convenience sample of community residents to collect information on their knowledge, attitudes, and practices regarding heartworms. Afterward, mosquito larvae were collected from the respondents' properties and adult mosquitoes were collected in both communities from surrounding wooded areas and residences of respondents. Mosquito species distribution and D immitis infection rates were determined. RESULTS Many residents (59% [57/96]) were unaware that mosquitoes transmit heartworms. Compared with non-dog owners, dog owners were significantly more likely to know about mosquito transmission, be concerned about heartworms, accurately estimate cost of treatment, and demonstrate willingness to pay for treatment. Most owners (71% [47/66]) administered heartworm preventives; those who did not cited lack of risk awareness, and cost was the least common reason. Of 28 mosquito species collected, Anopheles quadrimaculatus, Culex erraticus, Culex nigripalpus, Coquillettidia perturbans, Culiseta inornata, Aedes albopictus, and Aedes aegypti were positive for D immitis infection. CONCLUSIONS AND CLINICAL RELEVANCE Findings suggested that improved veterinary and public health messaging regarding the role of mosquitoes as vectors, higher cost of heartworm treatment versus prevention, and mosquito reduction and avoidance methods is needed.

The genetic diversity and structure of invasive species are affected by the time since invasion, but it is not well understood how. We compare likely the oldest populations of Aedes aegypti in continental North America with some of the newest to illuminate the range of genetic diversity and structure that can be found within the invasive range of this important disease vector. Aedes aegypti populations in Florida have probably persisted since the 1600‐1700s, while populations in southern California derive from new invasions that occurred in the last 10 years. For this comparison, we genotyped 1,193 individuals from 28 sites at 12 highly variable microsatellites and a subset of these individuals at 23,961 single nucleotide polymorphisms (SNPs). This is the largest sample analyzed for genetic structure for either region, and it doubles the number of southern California populations previously analyzed. As predicted, the older populations (Florida) showed fewer indicators of recent founder effect and bottlenecks; in particular, these populations have dramatically higher genetic diversity and lower genetic structure. Geographic distance and driving distance were not good predictors of genetic distance in either region, especially southern California. Additionally, southern California had higher levels of genetic differentiation than any comparably sized documented region throughout the worldwide distribution of the species. Although population age and demographic history are likely driving these differences, differences in climate and transportation practices could also play a role.

Invasive feral swine (Sus scrofa) are one of the most important wildlife species for disease surveillance in the United States, serving as a reservoir for various diseases of concern for the health of humans and domestic animals. Brucella suis, the causative agent of swine brucellosis, is one such pathogen carried and transmitted by feral swine. Serology assays are the preferred field diagnostic for B. suis infection, as whole blood can be readily collected and antibodies are highly stable. However, serological assays frequently have lower sensitivity and specificity, and few studies have validated serological assays for B. suis in feral swine. We conducted an experimental infection of Ossabaw Island Hogs (a breed re-domesticated from feral animals) as a disease-free proxy for feral swine to (1) improve understanding of bacterial dissemination and antibody response following B. suis infection and (2) evaluate potential changes in the performance of serological diagnostic assays over the course of infection. Animals were inoculated with B. suis and serially euthanized across a 16-week period, with samples collected at the time of euthanasia. The 8% card agglutination test performed best, whereas the fluorescence polarization assay demonstrated no capacity to differentiate true positive from true negative animals. From a disease surveillance perspective, using the 8% card agglutination test in parallel with either the buffered acidified plate antigen test or the Brucella abortus/suis complement fixation test provided the best performance with the highest probability of a positive assay result. Application of these combinations of diagnostic assays for B. suis surveillance among feral swine would improve understanding of spillover risks at the national level.