With the recent emergence of Oropouche virus (OROV) as a potential public health concern in the United States, the American Mosquito Control Association (AMCA) is collaborating with the CDC to collect surveillance data on its primary vector, Culicoides paraensis.

As part of this effort, we are seeking mosquito control districts willing to assist by deploying modified CDC light traps on a weekly basis. This will help us assess the distribution of potential OROV vectors across the country.

We have limited funding available through our grant to support the purchase of traps and other necessary supplies, if needed.

Attached you’ll find:

• A detailed protocol for the collection, storage, and shipment of biting midge samples
• Instructions for modifying standard CDC light traps for Culicoides collection
• A sample data sheet

If your district is able to participate, or if you know of another district or agency that might be interested, please contact Dan Markowski, AMCA Technical Advisor at 662-822-1270 or email at AMCA.TA@mosquito.org.

Culicoides Surveillance Protocol

Trapping Datasheet Template

Mosquito Trap PDF

G. Yamey and B. K. Titanji. 2025. New England J. Medicine. Perspective. DOI: 10.1056/NEJMp2501790

On July 6, 2020, during his first presidency, Donald Trump notified the United Nations secretary-general that the United States would withdraw from the World Health Organization (WHO). The withdrawal never happened because the process takes a year, as outlined in a 1948 joint resolution of Congress,1 and President Joe Biden reversed the decision on his first day in office. But Trump has done it again: on the day of his second inauguration, January 20, 2025, he issued an executive order saying the United States will withdraw from the WHO and pause the future transfer of U.S. funding to the organization. The order also recalls U.S. personnel working with the WHO in any capacity. [read more].

Note: Pathogens and vectors don’t respect political boundaries and these actions may have dire consequences for surveillance and control of communicable diseases, especially considering DOGE cuts to the US CDC and USAID.

Emerg Infect Dis. 2025;31(4):699-709.
https://doi.org/10.3201/eid3104.241520

Abstract
Viral encephalitis is often underreported and undiagnosed. To understand the potential causes of viral encephalitis in the state of Montana, USA, we examined the relative incidence of human infections for the California serogroup (CSG) of Orthobunyaviruses by screening random convenience serum samples obtained from different hospitals across Montana. We initially screened deidentified samples for neutralizing antibodies against Jamestown Canyon virus (JCV), a CSG virus that has caused encephalitis in Montana. We then analyzed JCV-positive samples for neutralization of other CSG viruses, and detected neutralizing antibodies against La Crosse virus, California encephalitis virus, and Trivittatus virus. We also found a high level of cross-reactivity, particularly between JCV and California encephalitis virus. Our findings indicate that the relative CSG virus infection rates in humans are quite high, between 21% and 40%. Clinicians should consider CSG viruses in differential diagnosis for cases of encephalitis of unknown etiology in Montana.

Note: CSG viruses are endemic to California, frequently isolated from endemic Aedes and Culiseta mosquitoes, and similar to this study sera from high risk groups have shown a high level of previous infection but little overt disease.

A ProMED-mail post
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Date: Tue 11 Mar 2025
Source: Diario de Yucatan [in Spanish, machine trans., abridged, edited]
https://www.yucatan.com.mx/mexico/2025/03/11/mas-casos-humanos-del-gusano-barrenador-devorador-de-hombres-en-mexico.html

More human cases of the man-eating screwworm in Mexico

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Mexico’s Ministry of Health (SSA) has reported new human cases of myiasis as the country faces outbreaks of the man-eating screwworm, or larvae of the fly _Cochliomyia hominivorax_, in livestock and even in pets in southeastern Mexico. The new cases of myiasis are 2 women from Chiapas; both were diagnosed in week 8 (16-22 Feb) of 2025, according to the Epidemiological Bulletin of week 9 (23 Feb-1 Mar) published yesterday, Monday, 10 Mar [2025] [https://www.gob.mx/cms/uploads/attachment/file/982667/sem09.pdf]. Both patients were detected just one month after Mexico reported its first human case of the man-eating screwworm, a woman from Campeche diagnosed in week 4 (19-25 Jan [2025]).

Note [from Kim Hung]: While NWS [New World Screwworm] is primarily a pest of animals, more importantly, cattle and deer, they can cause myaisis in humans. Their native range includes California when you look at the maps of where they were long ago. A couple of colleagues noted that if this trend continues, they can potentially reach the US this year, perhaps starting with Texas. Extra note – We have a related species in California that is not as pestiferous (in terms of myiasis, they eat dead tissue) – Cochliomyia macellaria. The adults look very similar with the distinguishing three stripes on the thorax, but there are some minor differences if we look carefully. There are keys available to distinguish between the two species if we need to confirm the ID at some point. Additionally, our colleagues in the USDA would be happy to help confirm ID if such a need arises. In other words, got a fly question? Bring ’em to me. =)

Note [WK Reisen]: The NWS was contained for years just north of the Darien Gap by the USDA and partners using SIT methods. The flies appear to have breached this containment and re-established themselves in Mexico. How will budget cuts to the USDA further facilitate this northern invasion?

A ProMED-mail post
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Date: Tue 18 Mar 2025 10:00 a.m. ET
Source: CDC Emergency Preparedness and Response [edited] 
View here

Summary
———
The Centers for Disease Control and Prevention (CDC) is issuing this Health Alert Network (HAN) health update to provide additional information to healthcare providers, public health departments, and the public about the ongoing risk of dengue virus (DENV) infections and updates to testing recommendations in the United States. Dengue activity remains high in some parts of the United States and globally, with many countries reporting higher-than-usual number of dengue cases in 2024 and 2025. Healthcare providers, public health departments, and the public are urged to continue to take steps to prevent, detect, diagnose, and respond to dengue as described in the June 2024 HAN Health Advisory (CDCHAN-00511) on dengue in the United States. Updates include the following:

1. Dengue virus transmission remains high in the Americas region, including in the US territories of Puerto Rico and the US Virgin Islands. Spring and summer travel coincide with the peak season for dengue in many countries, increasing the risk of both travel-associated and locally acquired cases in the United States.

2 Use the CDC DENV-1-4 real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay when dengue is the most likely diagnosis.

3. New resources are available for public health professionals including a job aid for reviewing medical records and guidance for investigating and responding to dengue cases in non-endemic areas of the United States.

Note: This Health Alert targets the awareness of the increased risk for dengue infection in travelers returning from the tropics.

Payne AF, et al. 2025. Emerg Inf Dis. Vol. 31, No. 3, March 2025
DOI: https://doi.org/10.3201/eid3103.241886

Abstract. Given recent outbreaks of Oropouche virus in Latin America and >100 confirmed travel-associated cases in the United States, we evaluated the vector competence of US mosquitoes, including Aedes albopictus, Culex quinquefasciatus, Culex pipiens, and Anopheles quadrimaculatus. Results with historic and recent isolates indicates transmission potential by these species is low [only 1/50 Cx. pipiens transmitted virus].

Note: Similar to the literature, a low percentage of females became infected, but practically all were not able to transmit. This and similar reports indicate the risk of secondary transmission by mosquitoes from imported cases is very low.

B.M. Mortola et al. 2025. J. Med. Entomol., tjaf001, https://doi.org/10.1093/jme/tjaf001

Abstract
The evolution of pyrethroid insecticide resistance in Culex tarsalis Coquillett is a growing concern in Northern California. Common mechanisms of resistance include the target-site mutation, kdr, and increased levels of detoxification enzymes, such as mixed-function oxidases, GSTs, and esterases. The goal of this study was to compare the prevalence of kdr mutations (L1014F and L1014S) and detoxification enzymes between pyrethroid susceptible and resistant Cx. tarsalis individuals. Individual mosquitoes, categorized by resistance status from permethrin bottle bioassays, were prepared for both molecular and enzymatic testing by separating the legs of a mosquito from the remaining body. Legs were used to test for the presence of kdr mutations, while the bodies were used to test for the activity of detoxification enzymes. The number of phenylalanine (F) alleles present at the kdr target-site as well as levels of GST were increased in mosquitoes that survived the bottle bioassay compared to those that were knocked down. Individuals with 2 F alleles and an active GST level greater than or equal to 0.052 µg/ml showed a higher survival rate than either mechanism independently demonstrating resistance to pyrethroids in Cx. tarsalis is likely the result of multiple resistance mechanisms acting collectively. Further work is needed to determine the interplay of multiple resistance mechanisms to achieve phenotype resistance in this mosquito species.

Note: Relating bottle assay results to specific resistance mechanisms is an important step in teasing apart the evolution of resistance.

Sebayang, BF, et al. 2025. PLoS Neglected Tropical Diseases https://doi.org/10.1371/journal.pntd.0012856

Abstract Background
The establishment of Aedes albopictus in the Torres Strait Islands in 2005 is a threat to dengue control in the islands and on mainland Australia. Attractive targeted sugar baits (ATSBs) have been proposed as a control strategy for outdoor mosquitoes like Ae. albopictus. The sugar feeding behaviours of Ae. albopictus was studied to ascertain the potential of ATSBs to mitigate the risk of Ae. albopictus invading mainland Australia from the Torres Strait Islands.

Methodology/Principal Findings
Aedes albopictus was sampled by sweep net collections in village and bushland habitats across two islands both in the mornings and afternoons. Samples were analysed to determine adult abundance as well as fructose prevalence and content by cold-anthrone test. Sampling stations were characterised by vegetation surveys and included the prevalence of flowers and fruit, and canopy cover. Among the 6,186 captured Ae. albopictus, the prevalence of fructose was 31.6% ± 1.4 in males and 30.5% ± 1.2 in females, with fructose averaging 62.9 µg (± 1.4) in fructose-positive Ae. albopictus.

Conclusions
Mosquito sex and collection time were associated with the abundance of Ae. albopictus as well as fructose prevalence and content in Ae. albopictus. Male and female Ae. albopictus exhibited sugar abundance and prevalence comparable to studies where ATSBs were effective suggesting that ATSBs could potentially reduce Ae. albopictus populations in the Torres Strait Islands.

Note: This study concluded that Ae. albopictus fed frequently on plant sugar and that ‘attractive targeted sugar baits’ may be useful for population suppression. Similar studies on Cx. tarsalis produced similar results, but developing an attractive bait for control proved problematic.

Date: Fri 7 Feb 2025
Source: PAHO/WHO Epidemiological Alert [edited] https://www.paho.org/en/documents/epidemiological-alert-risk-dengue-outbreaks-due-increased-circulation-denv-3-americas

The occurrence and magnitude of dengue outbreaks are usually associated with the introduction or increase in circulation of a serotype other than the one that previously predominated in an affected region. Given the risk of an increase in the circulation of DENV3 in the southern hemisphere of the Americas Region during the peak dengue season, the Pan American Health Organization / World Health Organization (PAHO/WHO) urges Member States to prepare for a possible increase in cases and ensure early diagnosis and timely care dengue and other arbovirus cases, in order to prevent severe cases and deaths associated with these diseases.

Summary of the situation in the Americas Region
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In 2024, there was a historic increase in dengue cases in the Americas Region with 13 027 747 cases reported by 50 countries and territories. Of this total, 6 906 396 were laboratory confirmed, 22 684 were characterized as severe dengue (0.17%), and 8186 were fatal cases (case fatality rate 0.063%). The countries that reported the highest proportion of cases were Brazil with 10 232 872 cases, Argentina with 581 559 cases, Mexico with 558 846 cases, Colombia with 320 982 cases, and Paraguay with 295 785 cases (1). Note: This detailed update provides country by country updates on the 2024 and present situation. The risk for further travel related cases persists.

L. Backus et al. email: J Foley jefoley@ucdavis.edu DOI: https://doi.org/10.4269/ajtmh.24-0497 

Abstract: A Rocky Mountain spotted fever (RMSF) epidemic has spread through the state of Baja California, Mexico over the last decade and a half, beginning in Mexicali, and subsequently to Tijuana and to Ensenada by 2018. In October of 2022, we surveyed dogs and homes in randomly selected Áreas Geoestadisticas Básicas (AGEBs) with and without reported human cases. Brown dog ticks (Rhipicephalus sanguineus sensu lato) were found on 33.9% of dogs and in the yards of 23.6% of homes. Homes from AGEBs with cases had over a 6-fold increased odds of ticks being present in the yard than AGEBs without reported cases. Both dogs that were permitted to roam and the presence of roaming dogs in the neighborhood were strongly associated with tick infestation of dogs and homes. No ticks or blood samples were polymerase chain reaction-positive for Rickettsia (R.) rickettsii, the causative agent of RMSF, although 54.6% of dogs were seropositive for spotted fever group rickettsiae, and 17.4% were seropositive for typhus group rickettsiae. R. massiliae and R. felis were detected in eight (1.3%) and 29 (4.8%) ticks, respectively; and R. felis was also detected in eight (4.6%) dog blood samples. Although the pathogenic potential of these other rickettsial species and their role in RMSF transmission remains unclear, our data on tick burdens in dogs and homes as risk factors for RMSF exposure provide further support to the pivotal need to reduce tick burdens and the numbers of roaming dogs to successfully manage the RMSF epidemic in northern Mexico.

Note: This paper clearly shows the importance of animal control and the importance of inspecting/quarantining imported dogs.

T.C. Moore, X. Tang, H.E. Brown [<heidibrown@arizona.edu>] Vector-Borne and Zoonotic Diseases https://doi.org/10.1089/vbz.2024.0072

Abstract
Background: Entomological surveillance indices are used to estimate the risk of West Nile virus transmission. To determine when and where to initiate mosquito control activities, integrated vector management programs establish action thresholds based on entomological surveillance indices. Herein, we examine the evidence from studies that investigated the quantitative relationship between entomological surveillance indices and human WNV cases using systematic review methods. Results: Across three databases, 5378 articles were identified. Using the selection criteria, 38 studies were included for study. Most articles explored entomological indices weekly and devised unique geographic scales to aggregate human and/or mosquito data. The most used models were logistic and negative binomial regression. Maximum likelihood estimates (MLEs) and vector index (VI) demonstrated the greatest ratio of number of positive results to number of times tested. Among all selected articles, 35 unique U.S. locations assessed MLE and/or VI. Human WNV infection had a significant association with MLE across 81.25% (13/16) of locations. VI showed successful performance across 80.00% (24/30) sites tested.

Conclusions:
This systematic review identifies methods for quantifying relationships between entomological and human WNV infection data. We found entomological surveillance indices applied to human WNV risk should include a measure of virus presence, such as MLE and VI. Model type and covariates were too variable to identify geographic or species-specific trends, though, when tested, including temperature, land cover, population density, and time improved the model. This study is meant to be informative and designed to assist public health agencies in seasonal WNV preparations but are not meant to be a panacea for all WNV surveillance challenges.

I. Mateescu & S. Lequime. 2025. J. Med. Entomol. 62(1), 19–28 https://doi.org/10.1093/jme/tjae134

Abstract [shortened]. An arthropod’s vectorial capacity summarizes its disease transmission potential. Studies have shown that mosquito-borne pathogens may alter important vectorial capacity traits of their mosquito vectors, thus directly impacting their transmission and epidemic potential. Here, we compile and discuss the evidence supporting dengue-mediated changes in Aedes aegypti (L.) and evaluate whether the observed effects represent an evolved trait manipulation with epidemiological implications. Dengue infection appears to manipulate essential traits that facilitate vector–host contact, such as locomotor activity, host-seeking, and feeding behavior, but the underlying mechanisms are not understood. Conversely, life-history traits relevant to vector population dynamics, such as survival, oviposition, and fecundity, appear to be negatively impacted by dengue virus. However, methodological disparities among studies render comparisons difficult and limit the ability to reach well-supported conclusions. This highlights the need for more standardized methods for research into changes in virus-mediated traits.

Note: This review paper focusses on dengue virus and aegypti, but may be relevant for other mosquito-borne arboviruses.

West Valley Mosquito and Vector Control District recently published their third paper on SIT. The latest paper discusses the efficacy of SIT targeted approach in the control of Aedes aegypti.

Click here to view

Tularemia — United States, 2011-2022. Rich SN, Hinckley AF, Earley A, et al. 2025. MMWR Morb Mortal Wkly Rep. 73(5152):1152-1156. http://dx.doi.org/10.15585/mmwr.mm735152a1

Tularemia is a rare nationally notifiable zoonosis, caused by the tier-1 select agent _Francisella tularensis_, that has been reported from all USA states except Hawaii. Clinical manifestations typically include fever and localized symptoms that vary by route of infection. The case fatality rate of tularemia is typically <2%, but can be higher depending on clinical manifestation and infecting strain. Tularemia is treatable with antimicrobials. During 2011-2022, a total of 47 states reported 2,462 tularemia cases, but 4 central states (Arkansas, Kansas, Missouri, and Oklahoma) accounted for 50% of all reported cases. Note: This report describes the epidemiology of reported cases and brings attention to this bacteria that has been reported infecting more than 250 species of wild and domestic animals. Infection is through insect or tick bites as well as contact with infected wild animals [e.g., cottontail rabbits] or immersion or ingestion of contaminated water. Ticks may be an important reservoir as they can maintain infection transstadially [pathogen remains within the vector from one life stage (“stadium”) to the next] and transovarially [transmission of a pathogen from an organism (as a tick) to its offspring by infection of eggs in its ovary].

Beyers et al. 2025. Evidence of Limited Laboratory Infection of Culex tarsalis (Diptera: Culicidae) by Usutu Virus. Vector-Borne and Zoonotic Diseases 25(1) https://doi.org/10.1089/vbz.2024.0054

Background: Usutu virus (USUV) is an emerging flavivirus, closely related to West Nile virus (WNV), that has spread into Europe from Africa. Since Culex tarsalis Coquillett is an important vector for WNV transmission in the United States, we tested the ability of USUV to replicate in and be transmitted by these mosquitoes. Materials and Methods: USUV was used to infect 3-4 day-old Cx. tarsalis with 5.6 to 7.5 log10 pfu/ml in goose bloodmeals. Saliva, heads, and bodies were collected on day 13 or 14 and analyzed by RT-qPCR for detection for USUV vRNA. Blotting paper punches were also collected daily to assess viral transmissibility. Results: The low and high dose blood meal resulted in 0% and 19.6% of the mosquitoes having established infections, respectively. All of the high dose females had a dissemination of USUV RNA to the heads and none of the filter papers had detectable USUV RNA, but five of the capillary saliva collections were positive, representing 45.5% of the infected mosquitoes.

Conclusions: Limited infection of Cx. tarsalis was observed when exposed to bloodmeals with greater than 10^7 pfu/mL of USUV, indicating this vector is not likely to have a key role in transmission of the virus. Note: USUV caused frequent epiornitics in blackbirds in Europe, but has not produced noticeable human disease, unlike WNV before its introduction into North America.

Clinical and Epidemiological Information Required for Lyme Disease Surveillance in a Low-Incidence State, California 2011–2017. Brummitt et al. 2024. Vector-Borne and Zoonotic Diseases [ahead of print]. https://doi.org/10.1089/vbz.2024.0043

Abstract [shortened]: Background: Between January 1, 2011, and December 31, 2017, over 12,000 case reports of Lyme disease (LD) were submitted to the California Reportable Disease Information Exchange for further investigation. The number of case reports has tripled compared to previous years, emphasizing the need for efficient estimation and classification methods. We evaluated whether estimation procedures can be implemented in a low-incidence state such as California to correctly classify a case of LD.

Objective: This study identified whether a minimum number of variables was sufficient to reliably classify LD cases in California and potentially reduce workload. Methods: To determine the relative value of diagnostic information, we compared five candidate logistic regression models that were used to classify cases based on information that varied in its degree of difficulty for collection. Results: Our results showed that automatically reported data were not sufficient, additional information such as a patient’s clinical presentation and travel history were necessary to improve the sensitivity of the models. Conclusion: This study demonstrated that both clinical and travel information were required to accurately classify a case of LD in California.

Note: These results were critical to interpret data from a passive case surveillance system to identify areas of high risk endemic transmission.

A scoping review to determine if adverse human health effects are associated with use of organophosphates for mosquito control. Tai, Z. et al. 2024. Journal of Medical Entomology, 2024, 1–11.

https://doi.org/10.1093/jme/tjae130

Abstract [shortened]. Organophosphate insecticides are widely used for adult mosquito control. Although proven effective in reducing mosquito populations and limiting arbovirus transmission, public concern exists regarding potential human health effects associated with organophosphate exposure. The aim of this scoping review was to describe any reported human health conditions associated with organophosphates during their use for adult mosquito control in the United States and Canada. Original peer-reviewed articles published in English language journals from 1 January 2000 to 22 May 2024 identified 6,154 screened articles. Following an independent review, 10 studies were identified that described human health conditions associated with organophosphate exposure during adult mosquito control applications. Of the 10 included studies, only two articles were published within the last 11 years (2013 to 22 May 2024). The included studies could not determine causality between exposure to adulticides and development of illness or adverse impacts. The available and limited evidence indicates that organophosphates can be used safely to control nuisance mosquitoes or mosquitoes that transmit arboviruses. Continued research regarding the human health effects associated with organophosphate applications for adult mosquito control could help evaluate the basis of the public’s concerns and inform public health decision-making.