Aedes albopictus is not an arbovirus aficionado when feeding on cynomolgus macaques or squirrel monkeys

Abstract

Viruses transmitted by Aedes mosquitoes (e.g., dengue [DENV], Zika [ZIKV]) have demonstrated high potential to spill over from their ancestral, sylvatic cycles in non-human primates to establish transmission in humans. Epidemiological models require accurate knowledge of the contact structure between hosts and vectors, which is highly sensitive to any impacts of virus infection in mosquitoes or hosts on mosquito feeding behavior. Current evidence for whether these viruses affect vector behavior is mixed. Here we leveraged a study on sylvatic DENV-2 and ZIKV transmission between two species of monkey and Aedes albopictus to determine whether virus infection of either host or vector alters vector feeding behavior. Engorgement rates varied from 0% to 100%, but this was not driven by vector nor host infection, but rather by the individual host, host species, and host body temperature. This study highlights the importance of incorporating individual-level heterogeneity of vector biting in arbovirus transmission models.

Keywords: biological sciences; microbiology; natural sciences; systems biology; virology.

Graphical abstract

Figure 1

Experimental infections of cynomolgus macaques and squirrel monkeys with sylvatic dengue or Zika virus In the overview (A), black represents uninfected vectors/hosts and red represents inoculated vectors or infected hosts. In the detailed sampling scheme (B), letters denote: C, serum sampled for cytokine quantification; M, mosquito feeding; V, serum sampled for viremia quantification; W, weight. A and B indicate cohorts, in the case of squirrel monkeys. The monkey and mosquito images are licensed from Shutterstock. ^†: only measured in control and DENV-2 infected cynomolgus macaques. ^‡: only measured for ZIKV-infected cynomolgus macaques. ^°: only measured for cohort B.

Figure 2

Engorgement rates of Aedes albopictus on day 0 of the experiments, depending on the mosquito inoculation status and NHP species (A) Probabilities of feeding predicted by the model per group (point), along with 95% confidence intervals, assuming a duration of mosquito exposure of 6 min (median of all exposures), with results of statistical comparisons indicated above brackets, with ns: p > 0.05, ∗∗∗: 0.0001 < p < 0.001, results of post hoc Wald tests (or z-test, details in Table S4). From left to right, $n$ (number of NHP) = 3, 5, 3, 15, 4, 7. (B) Raw data (one point = one NHP) colored by mosquito inoculation status (gray triangle: control, green circle: DENV-2, blue square: ZIKV), with one boxplot per group. Box boundaries indicate the 25th (bottom) and 75th (top) percentiles. The line within the box marks the median. Whiskers above and below the box indicate the 10th and 90th percentiles, respectively. Duration of mosquito exposure varies but is not shown here. The monkey images are licensed from Shutterstock. See also Tables S4–S6.

Figure 3

Engorgement rates of uninfected Aedes albopictus depending on NHP infection status and species (A) Probabilities of feeding predicted by the simple model per group (point), along with 95% confidence intervals, assuming a duration of mosquito exposure of 6 min (median of all exposures), with results of statistical comparisons indicated above brackets, with ns: p > 0.05, ∗∗: 0.001 < p < 0.01, ∗∗∗: 0.0001 < p < 0.001, results of post hoc Wald tests (or z-test, details in Table S7). From left to right, $n$ (number of batches of mosquitoes) = 36, 81, 33, 26, 60, 57. (B) Raw data (one point = a single batch of mosquitoes fed on a given NHP on a given day) colored by NHP infection status (gray triangle: control, green circle: DENV-2, blue square: ZIKV), with one boxplot per group. Duration of mosquito exposure varies but is not shown here. Data from day 28 excluded (see STAR Methods). (C) Raw data, same as (B) except that for infected groups, we restrict the data to the range of days where viremia was detected for each virus (days 1–14 for DENV-2, 1–8 for ZIKV). In (B) and (C), box boundaries indicate the 25th (bottom) and 75th (top) percentiles. The line within the box marks the median. Whiskers above and below the box indicate the 10th and 90th percentiles, respectively. The monkey images are licensed from Shutterstock. See also Tables S7–S9.

Figure 4

Relationship between host body temperature and Aedes albopictus engorgement rates, in cynomolgus macaques (left column) and squirrel monkeys (right column) Raw data (one point = one NHP on one day) colored by NHP infection status (gray triangle: control, green circle: DENV-2, blue square: ZIKV). Note that the same set of control animals are shown for same species experiments (A, C for cynomolgus macaques, B, D for squirrel monkeys). The duration of mosquito exposure varies but is not shown here. Data from day 28 excluded (see STAR Methods). The monkey images are licensed from Shutterstock. See also Figure S2 and Tables S10–S12.

Figure 5

Engorgement rates of Aedes albopictus on individual NHPs, normalized by duration of exposure, depending on monkey infection status and species One boxplot per NHP, colored by NHP infection status (gray: control, green: DENV-2, blue: ZIKV), with raw data (triangle: control, circle: DENV-2, square: ZIKV). Box boundaries indicate the 25th (bottom) and 75th (top) percentiles. The line within the box marks the median. Whiskers above and below the box indicate the 10th and 90th percentiles, respectively. Red points indicate feedings on animals that were detectably viremic or that resulted in transmission to mosquitoes. Data from day 28 excluded (see STAR Methods). The monkey images are licensed from Shutterstock. See also Figures S1 and S3.

Figure 6

Analysis of the relationship between repeated exposures to bites of uninfected mosquitoes and cytokine concentrations In control cynomolgus macaques, concentrations of cytokines EGF (A and C) and MIF (B and D) are significantly associated with the number of uninfected mosquitoes which engorged the day before (A and B) and in the last 7 days (C and D). Results from generalized additive mixed effect models, estimating an intercept per NHP. Thick black lines and shading show the population trends with uncertainty. Colored lines are individual fits. Fits for a given exposure variable (short-term or long-term) are computed with the other variable fixed (0 for short-term, 10 for long-term), which is why data points are not plotted (short-term and long-term variables varied concomitantly in the experiments). Note that y axis scales differ between cytokines (A and C vs. B and D) and that x axis scales differ between exposure variables (A and B vs. C and D). The monkey images are licensed from Shutterstock. See also Figures S4–S9.