Temperature-Mediated Effects on Mayaro Virus Vector Competency of Florida Aedes aegypti Mosquito Vectors

Abstract

Mayaro virus (MAYV) is an emerging mosquito-borne arbovirus and public health concern. We evaluated the influence of temperature on Aedes aegypti responses to MAYV oral infection and transmission at two constant temperatures (20 °C and 30 °C). Infection of mosquito tissues (bodies and legs) and salivary secretions with MAYV was determined at 3, 9, 15, 21, and 27 days post ingestion. At both temperatures, we observed a trend of increase in progression of MAYV infection and replication kinetics over time, followed by a decline during later periods. Peaks of MAYV infection, titer, and dissemination from the midgut were detected at 15 and 21 days post ingestion at 30 °C and 20 °C, respectively. Mosquitoes were able to transmit MAYV as early as day 3 at 30 °C, but MAYV was not detectable in salivary secretions until day 15 at 20 °C. Low rates of MAYV in salivary secretions collected from infected mosquitoes provided evidence supporting the notion that a substantial salivary gland barrier(s) in Florida Ae. aegypti can limit the risk of MAYV transmission. Our results provide insights into the effects of temperature and time on the progression of infection and replication of MAYV in Ae. aegypti vectors.

Keywords: Aedes aegypti; Mayaro; arbovirus; climate; per os infection.

Figure 1

(A) Distribution of MAYV in the Americas. (B) Potential transmission cycles of MAYV.

Figure 2

Schematic diagram of the experimental design.

Figure 3

Temperature influences on mosquito competence for MAYV. Mosquitoes were challenged with ingestion of MAYV-infected bloodmeal (7 log₁₀ PFUe/mL) for 1 h at 28 °C; then, engorged females were placed in separate environmental incubators (20 °C = low; 30 °C = high) for the remainder of the study. At 3, 9, 15, 21, and 27 dpi, mosquitoes (n = 30/time point) were anesthetized with CO₂, and their wings and legs were removed from their bodies, followed by a collection of salivary secretions. (A) MAYV susceptibility to infection (body), (C) disseminated infection (legs), and (E) transmission (salivary secretions) expressed in percentages. The kinetics of MAYV growth in mosquito tissues and salivary secretions were determined by qRT-PCR. (B) MAYV titer of body, (D) legs, and (F) salivary secretions, represented as (PFUe/mL). Each data point in (B,D,F) represents the kinetics of MAYV growth (titer) of individual mosquitoes. Gray data points in (B) represent mosquitoes with non-disseminated infection (i.e., MAYV infection limited to the midgut). Numbers in brackets above bars indicate the total number of mosquitoes positive for MAYV. Horizontal lines indicate the mean ± SEM. Statistical significance was determined using logistic regression analysis and two-way ANOVA for MAYV infection measurements and titers, respectively. p-values were corrected for multiple comparisons. Asterisks (*) denote significant differences; p < 0.05.