Anomalous phenology of Ixodes scapularis (Ixodida: Ixodidae) in Mississippi

The blacklegged tick, Ixodes scapularis Say, is one of the most important vectors of tick-borne disease agents in North America. Accordingly, it is crucial to know this species local composition, abundance, and seasonality (phenology) to help prevent tick-borne illnesses. The phenology of adult I. scapularis is reported in the scientific literature from October through May. Data from previous research in Mississippi have all supported this time frame for adult blacklegged tick activity. However, in this study, we report a collection of 13 I. scapularis from 9 widely separated areas in Mississippi during the summer and early fall of 2022 (June, July, and September). These findings are remarkable, even enigmatic, and should prompt further investigation.

Distribution of Culex coronator in the USA

In 1920, Culex coronator was reported from San Benito, Texas, and later in Arizona, New Mexico, and Oklahoma. In 2005, this species was reported to be spreading across the southeastern USA. Now reported in 14 states, it has been found as far north as northern Oklahoma; Memphis, TN; and Suffolk, VA. The public health significance of Cx. coronator is not firmly established, even though it has been implicated as a potential vector of several arboviral diseases. This study aims to document additional Cx. coronator county-level records, to provide information about its continued expansion across the southern USA, and to provide a short research update into its vector potential. Data acquired through multistate collaborations and author collections resulted in 146 new county records from Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, and Texas. No new county records were presented for Arizona, New Mexico, Tennessee, or Virginia, which had previously reported this species. With these new data, this species has been documented in 386 counties in 14 states of the continental USA.

Seasonality of Aedes albopictus in North and Central Mississippi

Container-breeding mosquitoes are increasingly important in public health due to recent outbreaks of Zika virus, chikungunya, and dengue. This paper documents seasonality of the most prevalent container-breeding mosquito species in Mississippi-Aedes albopictus. Ten sites in 5 counties in both northern and central Mississippi (20 sites, 10 counties total) were sampled by larval dipping and oviposition traps biweekly from September 2016 to June 2019, totaling 22 months and potentially yielding 440 egg or larval collections. However, 22 collections were missed due to inclement weather and personnel issues during the study period, so actually only 418 site visits were performed. Sites were chosen to maximize chances of finding Ae. albopictus. Of the total 1,310 mosquito larvae collected during the study period, 717 larvae and 50 positive egg papers belonged to Ae. albopictus. Aedes albopictus was found in all 10 northern and central counties. No eggs were collected at any of the sites from December through February, although larvae were occasionally collected during that time frame. This study demonstrates that Ae. albopictus is active in central and northern Mississippi beginning in March each year and continuing through November or December. There is little activity during the coldest months of the year (January and February). These data represent the first extensive analysis of Ae. albopictus seasonality in Mississippi, and as such, allow for better public health awareness of diseases transmitted by this species and design of more effective vector control programs.

Disaster Vector Control in Mississippi After Hurricane Katrina: Lessons Learned

Hurricane Katrina devastated the Mississippi Gulf Coast on August 29, 2005, causing an ecological disaster. Mississippi State Department of Health (MSDH) entomologists established a vector control program in affected areas with the following objectives: 1) helping local vector control agencies reestablish services, 2) performing mosquito surveillance, and 3) establishing mosquito larviciding and adulticiding where necessary. The MSDH personnel also helped write Action Request Forms requesting assistance from the Federal Emergency Management Agency (FEMA) for increased ground spraying in the 6 lower counties. Mosquito surveillance was conducted daily for 2 wk after the storm, then weekly for another month. Sanitation lagged, with people using makeshift latrines or simply piles of rubbish for bathrooms. Filth flies contaminated food and food surfaces. Responders lived in tent cities, many allowing filth fly access. Approximately 2 wk after hurricane landfall, due to increasing mosquito numbers, MSDH entomologists requested FEMA for an aerial spraying of insecticide to reduce nuisance mosquito biting in the area. A private vendor made 1 application of naled (Dibrom®) insecticide in the 3 coastal counties, yielding over 90% control in entire counties in 1 night. No complaints or medical or environmental problems from the increased ground spraying and aerial spraying were reported. Overall, important lessons in disaster vector control were learned, including how to work effectively with Centers for Disease Control, FEMA, and the US Public Health Service personnel, how to manage the public relations/educational aspects, and how to avoid or mitigate political interference in the disaster response.

Oviposition Responses and Potential Larval Control Methods of Aedes albopictus (Diptera: Culicidae) in Downspout Extensions

Aedes albopictus (Skuse) is an important invasive species and vector of several important arboviruses across the globe. This species uses small water-holding cryptic containers as egg laying sites, which pose serious challenges to effective control of adult mosquito populations. Herein, we examined the response of gravid female Ae. albopictus to various features of common downspout extension tubes associated with human dwellings and the effectiveness of control efforts to eliminate larvae. Controlled field trials quantified oviposition in 1) extensions versus rubber bowls meant to mimic other container types, 2) among different shapes and materials of extensions, and 3) among different colors of extensions. We also investigated how flushing and use of Bti larvicides could control larvae. Females were more likely to lay eggs in flat plastic or metal extensions compared to rubber bowls. Eggs were also more plentiful in flat plastic extensions versus either corrugated or metal, and dark brown corrugated extensions had more eggs compared to tan or white. Flushing reduced nearly all larvae when the extensions were properly angled, and applications of Bti pellets or dunks were effective at killing most larvae. We show that dark extensions were preferred over other colors, and that larvae can be effectively removed with minimal effort. However, effective control will likely only come from better education of the public about proper installation of extensions.

Insecticide Resistance Testing of Culex quinquefasciatus and Aedes albopictus from Mississippi

Data on insecticide resistance in mosquitoes from Mississippi are reported. Mosquitoes were collected from June through October 2017 from 28 cities in Mississippi and included wild-caught Culex quinquefasciatus Say obtained as egg rafts (reared to adults), and Aedes albopictus (Skuse) collected as larvae (reared to adults). The Centers for Disease Control and Prevention (CDC) bottle bioassay protocol was utilized. Thirty-six populations of Cx. quinquefasciatus were tested for malathion resistance from 24 cities; 22 of them (61.1%) met the World Health Organization criteria as resistant, and the remaining 14 (38.9%) were classified suspected resistant. Forty-one populations of Cx. quinquefasciatus were also tested from 24 cities for resistance to permethrin, and of these, 18 populations (43.9%) were susceptible, 13 (31.7%) were resistant, and 10 (24.4%) were suspected resistance. Eighteen populations of Ae. albopictus were collected from 10 cities in Mississippi for resistance testing to malathion; 5 populations were susceptible (27.8%), 5 were resistant (27.8%), and 8 (44.4%) suspected resistant. Sixteen populations of Ae. albopictus were tested from 10 cities for resistance to permethrin and none were resistant.

A Statewide Survey for Container-Breeding Mosquitoes in Mississippi

Container-breeding mosquitoes are important in public health due to outbreaks of Zika, chikungunya, and dengue viruses. This paper documents the distribution of container-breeding mosquito species in Mississippi, with special emphasis on the genus Aedes. Five sites in each of the 82 Mississippi counties were sampled monthly between May 1 and August 31, 2016, and 50,109 mosquitoes in 14 species were collected. The most prevalent and widely distributed species found was Ae. albopictus, being found in all 82 counties, especially during July. A recent invasive, Ae. japonicus, seems to be spreading rapidly in Mississippi since first being discovered in the state in 2011. The most abundant Culex species collected were Cx. quinquefasciatus (found statewide), Cx. salinarius (almost exclusively in the southern portion of the state), and Cx. restuans (mostly central and southern Mississippi). Another relatively recent invasive species, Cx. coronator, was found in 20 counties, predominantly in the southern one-third of the state during late summer. Co-occurrence data of mosquito species found in the artificial containers were also documented and analyzed. Lastly, even though we sampled extensively in 410 sites across Mississippi, no larval Ae. aegypti were found. These data represent the first modern statewide survey of container species in Mississippi, and as such, allows for better public health readiness for emerging diseases and design of more effective vector control programs.

Use of the VectorTest for Advanced Warning of Human West Nile Virus Cases in Mississippi

West Nile virus (WNV) continues to persist in Mississippi; 2012 was the worse year for human infections, with a total of 247 reported human cases and five deaths. Public health officials are keenly interested in ways to detect WNV in advance in their jurisdictions, so they can implement appropriate and timely mosquito control in affected areas. A total of 40,312 female Culex quinquefasciatus mosquitoes were collected by gravid traps in Mississippi in 2013 and 2014 and tested by VectorTest, a rapid immunochromatographic assay (“dip-stick” test) that is a highly specific and effective rapid threat assessment tool. This study evaluated if and to what extent VectorTest could provide advanced warning of impending human WNV cases in a specific area. These data were examined with regard to date of onset of human WNV cases to determine the predictive value of VectorTest for WNV activity. Both years, positive mosquito pools appeared before the vast majority (87.2%) of reported human cases. Overall, in 27 out of 37 human WNV cases (73.0 %) occurring in our study sites, there was an average advanced warning of 26 days (range 11–53 days) as indicated by positive mosquito collections near the patient’s home. This operational health department study, although somewhat limited, reveals that mosquito sampling and testing can inform public health and mosquito control personnel of WNV activity in an area and of impending human cases.

Chikungunya in Mississippi: The Health Department Response to Imported Cases

Chikungunya (CHIK), a newly recognized mosquito-borne disease in the Western Hemisphere, has resulted in well over a million cases since December 2013. Only about a dozen locally-acquired cases thus far have been reported in the U. S. (Florida), but approximately 1500 imported cases have been seen in returning travelers from the Caribbean and Central and South America. Public health officials are concerned that imported cases may lead to infection of local mosquitoes and, thus disease transmission. This paper documents 9 confirmed CHIK cases in Mississippi: 5 resulting from travel to the Dominican Republic, 2 from Haiti, 1 from Honduras, and 1 from Puerto Rico. In addition, the Mississippi State Department of Health response to those cases is presented and discussed.

First record of Aedes japonicus japonicus in Mississippi

In July 2011, 7 late-stage larvae of Aedes japonicus japonicus were collected from a 5-gal bucket located behind a house in Fulton, MS. Three of the larvae were reared to the adult stage, with the remaining retained in 70% ethanol. Fifteen subsequent attempts over the next month to collect specimens by larval dipping in artificial containers at the property and surrounding towns in 3 adjacent counties all failed to produce any additional Ae. j. japonicus.

An annotated list of the mosquitoes (Diptera: Culicidae) of Mississippi

There has been no previous systematic statewide study of mosquitoes in Mississippi. This survey, resulting in the collection of over 400,000 specimens, was conducted by the authors from 2003 to 2007 throughout much of the state using CO2-baited CDC light traps and larval dipping. In addition, a health department contract mosquito surveillance technician collected several thousand specimens from the state from 2001 to 2003. Lastly, specimens housed at the Mississippi State University Entomological Museum, obtained from previous surveys, were included as vouchers for species occurring in the state. The collection records and literature show 60 species as occurring or having occurred in Mississippi. Voucher specimens representing 57 of the 60 species discussed are deposited in the Mississippi Entomological Museum or in the U.S. National Museum of Natural History (USNM), Washington, D.C.

Notes on the ecology of Culex coronator Dyar and Knab, in Mississippi

CDC light-trap collections and larval dipping conducted during 2004 and 2005 revealed Culex coronator firmly entrenched in 10 counties in central and south Mississippi. A total of 3,307 specimens (2,200 adults, 1,107 larvae) of Cx. coronator have been collected in Mississippi. Notes on breeding sites and seasonality are presented and discussed. It is likely that the Mississippi population of Cx. coronator is contiguous with the one previously known from southern Texas, because specimens have been collected in Harris County, TX over the last few years, and were also found in Louisiana in 2004. Establishment of this population of a nonnative mosquito in Mississippi reveals how apparently easy it is for such events to happen.