Seasonal population dynamics of the primary yellow fever vector Haemagogus leucocelaenus (Dyar & Shannon) (Diptera: Culicidae) is mainly influenced by temperature in the Atlantic Forest, southeast Brazil

Abstract

BACKGROUND Southeast Brazil has recently experienced a Yellow Fever virus (YFV) outbreak where the mosquito Haemagogus leucocelaenus was a primary vector. Climatic factors influence the abundance of mosquito vectors and arbovirus transmission. OBJECTIVES We aimed at describing the population dynamics of Hg. leucocelaenus in a county touched by the recent YFV outbreak. METHODS Fortnightly egg collections with ovitraps were performed from November 2012 to February 2017 in a forest in Nova Iguaçu, Rio de Janeiro, Brazil. The effects of mean temperature and rainfall on the Hg. leucocelaenus population dynamics were explored. FINDINGS Hg. leucocelaenus eggs were continuously collected throughout the study, with a peak in the warmer months (December-March). The climatic variables had a time-lagged effect and four weeks before sampling was the best predictor for the positivity of ovitraps and total number of eggs collected. The probability of finding > 50% positive ovitraps increased when the mean temperature was above 24ºC. The number of Hg. leucocelaenus eggs expressively increase when the mean temperature and accumulated precipitation surpassed 27ºC and 100 mm, respectively, although the effect of rainfall was less pronounced. MAIN CONCLUSIONS Monitoring population dynamics of Hg. leucocelaenus and climatic factors in YFV risk areas, especially mean temperature, may assist in developing climate-based surveillance procedures to timely strengthening prophylaxis and control.

The Absence of Yellow Fever in Asia: History, Hypotheses, Vector Dispersal, Possibility of YF in Asia, and Other Enigmas

“…leucocelaenus and possibly of Hg. janthinomys during dry season in the forest fragments was observed [163,225]; and a long-term study revealed that YFV persisted in the same forest area (in the interface environment) for at least 3 years consecutively [226].…”

Oviposition activity of Haemagogus leucocelaenus (Diptera: Culicidae) during the rainy and dry seasons, in areas with yellow fever virus circulation in the Atlantic Forest, Rio de Janeiro, Brazil

“…The sampling locations are shown in (Fig 1). The state of Rio de Janeiro is characterized by having a hot and rainy climate between November and April (rainy period) and a cold and dry climate between May and October (dry period) [20].…”

Oviposition behavior of wild yellow fever vector mosquitoes (Diptera: Culicidae) in an Atlantic Forest fragment, Rio de Janeiro state, Brazil

“…However, the other vector species were not statistically significantly influenced by the climatic variables tested. Haemagogus leucocelaenus fluctuates in number of individuals throughout the year; however, the uninterrupted observation of eggs from this species in breeding sites illustrates that it maintains hematophagy activity throughout the studied months, regardless of climatic conditions 9 , 38 . This pattern of monthly egg collection and constant activity of Hg.…”

“…Weather conditions can also play a role in the vertical selection of oviposition sites 16 . Some studies have been shown that higher average temperatures favor mosquito eggs hatching, accelerates larval development 33,37 , and consequently speeds the YFV transmission 38 . Higher average temperatures also increase the frequency of biting activities 33 and reduce the duration of YFV incubation in the vector, which is the time elapsed between the mosquito's infectious blood meal and the arrival of these viral particles in its salivary glands 39,40 .…”