Merilyn J Geary

The influence of microfilaria! density of dog heartworm Dirofilaria immitis on infection rate and survival of Aedes notoscriptus and Culex annulirostris from Australia

Abstract. The mosquitoes Aedes notoscriptus and Culex annulirostris, previously shown to be competent vectors of Dirofilaria immitis, were allowed to feed on dogs with densities of microfilariae ranging from 2665 to 33,055 microfilariae/ml. Filaria developed in both species at a similar rate independent of the initial microfilarial density. Cx annulirostris ingested more microfilariae although the number of developing larvae was consistently greater in Ae. notoscriptus; one female Ae. notoscriptus carried sixty‐two third‐stage larvae 10 days after feeding, although no more than twelve were found in Cx annulirostris. The mortality rate of Ae. notoscriptus in the first 3 days of filarial development was related to increasing microfilarial density, and was greater than that of Cx annulirostris, which quickly reduced its worm load and survived with fewer third‐stage larvae but for longer than Ae. notoscriptus. The vector efficiency index was higher at all microfilarial densities for Ae. notoscriptus, but its survival was much reduced, and therefore Cx annulirostris may be the more effective vector in localities where dogs have very high parasitaemias.

Encasing Mattresses in Black Plastic Will Not Provide Thermal Control of Bed Bugs, Cimex spp. (Hemiptera: Cimicidae)

The suggestion that bed bug (Cimex spp.; Hemiptera: Cimicidae)-infested mattresses wrapped in black plastic and exposed to sunlight will be heated sufficiently to kill the bed bugs was tested. Two types of mattresses were tested: a thin mattress of solid foam rubber and a thick multilayered inner spring mattress. Temperature probes were placed on both upper and lower sides of the mattresses, which were wrapped in black plastic and placed outside on a summer day for >9 h wherein the ambient temperature peaked at 36.5 degrees C. The maximum recorded temperature on the upper (sun-exposed) sides was 85 degrees C for both mattresses, whereas lower side temperatures for the thick mattress never exceeded 35 degreesC, and some areas of the thin mattress failed to exceed 36.50C. Therefore, with published thermal death points of 40-45 degrees C depending on exposure time, and opportunities for bed bugs to avoid lethal temperatures by retreating from hot zones, this technique seems to be not suitable for bed bug management.

The susceptibility of the mosquitoes Aedes notoscriptus and Culex annulirostris to infection with dog heartworm Dirofilaria immitis and their vector efficiency

Abstract. The mosquitoes Aedes notoscriptus (Skuse) and Culex annulirostris Skuse were fed on a dog infected with Dirofilaria immitis (Leidy) and a blood parasite count of approximately 5000 microfilaria per ml. Cx annulirostris ingested almost 4 times as much blood and almost 4 times as many microfilariae as Ae.notoscriptus (mean 26.0 compared to 6.6). Attrition of the filarial numbers occurred primarily within the midgut during the first 24 h following ingestion and was greater in Cx annulirostris than Ae. notoscriptus. Aedes notoscriptus sustained development of almost 8 times as many third‐stage infective larvae as Cx annulirostris (mean of 3.8 compared to 0.5), and thus had a vector efficiency index of 57.6 compared to 1.9 for Cx annulirostris. In a series of investigations Ae. notoscriptus has now been shown to be an important vector for dog heartworm in southern Australia and may be a significant factor in the apparent burgeoning of the disease.