Identifying Knowledge Gaps through the Systematic Review of Temperature-Driven Variability in the Competence of Aedes aegypti and Ae. albopictus for Chikungunya Virus

Abstract

Temperature is a well-known effector of several transmission factors of mosquito-borne viruses, including within mosquito dynamics. These dynamics are often characterized by vector competence and the extrinsic incubation period (EIP). Vector competence is the intrinsic ability of a mosquito population to become infected with and transmit a virus, while EIP is the time it takes for the virus to reach the salivary glands and be expectorated following an infectious bloodmeal. Temperatures outside the optimal range act on life traits, decreasing transmission potential, while increasing temperature within the optimal range correlates to increasing vector competence and a decreased EIP. These relatively well-studied effects of other Aedes borne viruses (dengue and Zika) are used to make predictions about transmission efficiency, including the challenges presented by urban heat islands and climate change. However, the knowledge of temperature and chikungunya (CHIKV) dynamics within its two primary vectors-Ae. aegypti and Ae. albopictus-remains less characterized, even though CHIKV remains a virus of public-health importance. Here, we review the literature and summarize the state of the literature on CHIKV and temperature dependence of vector competence and EIP and use these data to demonstrate how the remaining knowledge gap might confound the ability to adequately predict and, thus, prepare for future outbreaks.

Keywords: Aedes aegypti; Aedes albopictus; EIP; EIT; chikungunya; extrinsic incubation period; extrinsic incubation temperature; temperature; transmission.

Figure 1

Out of the 8 publications examining the temperature dependence of CHIKV vector competence/EIP, (A) the frequency at which investigations were performed over each temperature category; (B) the frequency at which each mosquito species was investigated; (C) frequency of data at each recorded day post exposure according to vector species and the metric (dissemination or transmission).

Figure 2

The average rate of dissemination (black circles) or transmission (gold diamonds) for each species across the combined temperature categories. Size of the points represents the number of data points at each time point/temperature across all 8 studies. V means variable (fluctuating) temperature with a mean in that temperature class.

Figure 3

Functions fitted to available data of dissemination rates at each timepoint for each of the six scenarios considered (EITClass–species combinations). Y-axis is the percent dissemination and day is the day post exposure of mosquitoes from literature. See Table 3 for details about the functional forms and parameters for each scenario.

Figure 4

The probability of autochthonous transmission (upper) and number of infectious mosquitoes (lower) for CHIKV resulting from 1000 transmission simulations considering the EIP_MAX for the respective EITClass in Ae. aegypti.

Figure 5

The probability of autochthonous transmission (upper) and number of infectious mosquitoes (lower) for CHIKV resulting from 1000 transmission simulations considering the EI_MAX for the respective EITClass in Ae. albopictus.

Figure 6

The probability of autochthonous transmission (upper) and number of infectious mosquitoes (lower) for CHIKV resulting from 1000 transmission simulations considering the EIP₅₀ for the respective EITClass in Ae. albopictus.

Figure 7

Summary of the available data regarding temperature dependence of CHIKV titer in Ae. albopictus.