Identification of Avian Malaria (PlasmodiumSp.) and Canine Heartworm (Dirofilaria immitis) in the Mosquitoes of Tennessee

Abstract

Plasmodium reticulum, the causative agent for avian malaria (a protozoan), and Dirofilaria immitis, the causative agent for canine heartworm (a filarial nematode), are 2 obligate parasites transmitted by mosquitoes. The objective of this project was to identify whether either parasite was present in Tennessee mosquitoes and to illustrate the need for collecting spatial and temporal vector-parasite data. During 2012, mosquitoes were collected from the East Tennessee Research and Education Center (ETREC) in eastern Tennessee and the Ames Plantation Research and Education Center (AMES) in western Tennessee using CO(2) traps and gravid traps. Once mosquitoes were identified to species, their heads and thoraces were pooled in groups of ≤10, and the entire pool underwent DNA extraction and parasite amplification via polymerase chain reaction (PCR) for Plasmodium and Haemoproteus parasite DNA (cytochrome b) and for Dirofilaria species DNA (internal transcribed spacer-2 ribosomal DNA). All positive PCR amplicons were bidirectionally sequenced to confirm positivity and to identify the potential parasite genotype. This approach resulted in 762 mosquito pools, 150 pools from AMES and 612 pools from ETREC. In total, 3,260 mosquitoes were collected, representing 28 mosquito species. The 3 abundant genera were Culex (2,440 specimens, 74.8%), Aedes (720, 22.1%), and Anopheles (85, 2.6%). The remaining specimens included 13 Psorophora, 1 Orthopodomyia signiferia, and 1 Coquillettidia perturbans. Of the 150 pools from AMES, 1 pool (0.7%) was positive for avian malaria and 12 pools (8.0%) were positive for canine heartworm. Of the 612 pools from ETREC, 61 pools (10.0%) were positive for avian malaria and 8 pools (1.3%) were positive for canine heartworm. Positive pools for both Plasmodium and Dirofilaria were primarily Culex pipiens and occurred later in the season. The confirmation of the agents for avian malaria and canine heartworm illustrates the need for concurrent spatial and temporal studies using different trapping methods. The confirmation of avian malaria and canine heartworm in Tennessee illustrates the need for concurrent spatial and temporal studies. Future studies incriminating the potential vector populations will begin to unravel the complex relationships that intimately tie together hosts, vectors, and parasites. Results provide a significant contribution to the knowledge of the diversity of mosquito parasites present in Tennessee, and the presence of positive field populations warrants additional research exploring the environmental factors contributing to transmission.

Mosquito diversity and dog heartworm prevalence in suburban areas

“…Given the lower probability of D. immitis-positive mosquitoes noted in suburban areas, our focus on sampling mosquitoes predominantly in suburbia could have resulted in lower overall within-mosquito prevalence rates than what has been reported in other studies sampling in more rural landscapes (e.g. [39]). We found that two mosquito diversity metrics were positively correlated with heartworm prevalence within dogs at the zip code level.…”

Avian Plasmodium in Eastern Austrian mosquitoes

“…In France, looking at the same mosquito species, prevalences ranging from 0% (February) to 15.8% (October) were observed [ 21 ]. A study in the USA, looking at different mosquito species, found 10% of 61 pools positive [ 37 ]. In studies in Japan, prevalence ranged from 14.3 to 23.9% depending on area and examined mosquito species [ 38 – 40 ].…”

Avian malaria parasites in the last supper: identifying encounters between parasites and the invasive Asian mosquito tiger and native mosquito species in Italy

“…Furthermore, avian malaria parasites have been isolated from wild Ae. albopictus mosquitoes, but usually showing low prevalence of infection [ 32 - 34 ]. Also, some studies have reported the absence of Plasmodium in Ae.…”