Recent evidence supports a role for genetics in autism, but other findings are difficult to reconcile with a purely genetic cause. Pathological changes in the cerebellum in autism are thought to correspond to an event before 30-32 weeks gestation. Our purpose was to determine whether there is an increased incidence of stressors in autism before this time period. Surveys regarding incidence and timing of prenatal stressors were distributed to specialized schools and clinics for autism and Down syndrome, and to mothers of children without neurodevelopmental diagnoses in walk-in clinics. Incidence of stressors during each 4-week block of pregnancy was recorded. Incidence of stressors in the blocks prior to and including the predicted time period (21-32 weeks gestation) in each group of surveys was compared to the other prenatal blocks. A higher incidence of prenatal stressors was found in autism at 21-32 weeks gestation, with a peak at 25-28 weeks. This does support the possibility of prenatal stressors as a potential contributor to autism, with the timing of stressors consistent with the embryological age suggested by neuroanatomical findings seen in the cerebellum in autism. Future prospective studies would be needed to confirm this finding.

We present a simplified method for the collection of mosquito saliva to determine Culex pipiens quinquefasciatus transmission of West Nile virus that can be used for experiments requiring large sample sizes.

Culex pipiens quinquefasciatus were fed blood containing either 7.0 ± 0.1 logs plaque-forming units (pfu)/ml (high dose) or 5.9 ± 0.1 logs pfu/ml (low dose) of West Nile virus and held at extrinsic incubation temperatures (EIT) of 28°C or 25°C. Approximately 20 mosquitoes per dose were collected after incubation periods (IP) of 4, 6, 8, and 12 days postinfection (dpi). Infection rates were influenced by EIT and virus dose but not by IP. Body titer was significantly higher for mosquitoes fed the high dose and held at 28°C at the later IPs (6, 8, and 12 dpi). However, leg titer was significantly higher for mosquitoes at the later IPs but did not differ between EITs or doses. Because infection rates varied with EIT and dose, there is likely a midgut infection barrier influenced by these factors that is not influenced by IP. Dissemination rates were influenced by all 3 factors consistent with the presence of a midgut escape barrier. Dissemination rate, body titer, and leg titer were dependent on IP, indicating the need to investigate multiple time points in vector competence studies to elucidate critical events in infection and dissemination. KeywordsCulex pipiens quinquefasciatus; West Nile virus; dose; vector competence; temporal progression West Nile virus (WNV, family Flaviviridae, genus Flavivirus) is cycled between wild birds and ornithophilic mosquitoes in the genus Culex (Hayes 1989, Day 2005. Culex pipiens quinque-fasciatus Say has been found infected with WNV in the field (Rutledge et al. 2003, Godsey et al. 2005, is a competent laboratory vector of WNV (Sardelis et al. 2001, Goddard et al. 2002, and is considered an important WNV vector in the USA.Vector competence is influenced by both extrinsic and intrinsic factors (Hardy et al. 1983). Extrinsic factors include extrinsic incubation temperature (EIT) (Hardy et al. 1983, Dohm et al. 2002 and virus dose (Kramer et al. 1981). Biological factors include mosquito species (Goddard et al. 2002), mosquito population (Richards et al. 2009), and virus strain (Moudy et al. 2007). Extrinsic and intrinsic factors may also influence the extrinsic incubation period (EIP) and affect vector competence (Hardy et al. 1983, Dohm et al. 2002, Reisen et al. 2006, Kilpatrick et al. 2008. The EIP begins when a virus is ingested with a blood meal. The virus infects mosquito midgut epithelial cells and disseminates out of the midgut, and the EIP ends when the virus is transmitted to a susceptible host. Mosquitoes were bloodfed as described elsewhere (Richards et al. 2007) with the exception that the virus used was freshly propagated in Vero cell culture. Mosquitoes were allowed to feed for 30 min on cotton pledgets soaked with a high or low dose of WNV mixed with citrated bovine blood (Hemostat, Dixon, CA) that had been warmed (35°C) for 10 min. Virus doses used were within the range of viremias commonly found in WNV-infected birds in Florida (Komar et al. 2003). Two aliquots (0.1 ml each) of the heated blood were placed into separate tubes of 1 ml of BA-1 diluent prio...