Between April and September 2017, blood samples were collected from 344 randomly selected
dogs older than 1 year in 180 settlements of 19 counties in Hungary. The dogs lived
exclusively outdoors, had never travelled and had neither been examined for Dirofilaria
infection nor treated against mosquitoes with insecticides or/and filarioid worms
with macrocyclic lactones. Dirofilaria infection was examined with a modified Knott's
test for microfilariae, DiroCHEK®, for the presence of D. immitis antigen, as well
as by multiplex and conventional PCR. Altogether, 77 (22.4%) dogs living in 58 settlements
of 17 counties were found to be infected with one or both Dirofilaria species based
on the PCR techniques. Twenty-eight (8.1%) and 38 (11.1%) dogs were infected with
D. immitis and D. repens, respectively. Coinfections were recorded in 11 samples (3.2%)
collected in 11 locations of 8 counties. The results confirmed that both dirofilarioses
are endemic in dogs and the eastern areas of the country are hyperendemic for heartworm
disease. Temperature showed a significant association with the prevalence of D. immitis
(OR 2.41, 95% CI 1.24-4.86, p = 0.012) but not with that of D. repens (OR 1.37, 95%
CI 0.78-2.47, p = 0.286). The prevalence of neither D. immitis (OR 0.99, 95% CI 0.98-1.00,
p = 0.213) nor D. repens (OR 1.01, 95% CI 0.99-1.01, p = 0.094) showed a significant
correlation with precipitation. The number of yearly growing degree days (GDD) based
on the lifecycle of Dirofilaria in mosquitoes ranged between 3.73 and 7.57 for the
Hungarian districts. The GDD showed a significant positive association with the prevalence
of D. immitis (OR 2.38, 95% CI 1.43-4.15, p = 0.001) and a non-significant positive
relationship with that of D. repens (OR 1.25, 95% CI 0.83-1.95, p = 0.291).
