Laboratory Selection and Assessment of Resistance Risk in Drosophila suzukii (Diptera: Drosophilidae) to Spinosad and Malathion

Drosophila suzukii (Matsumura) is one of the most economically important pests of soft-skinned fruits worldwide. Repeated insecticide applications commonly used to prevent fruit infestations increase the risk of resistance development in D. suzukii. Assessment of resistance risk in D. suzukii using artificial selection can be valuable in developing proactive resistance management strategies to retain susceptibility in the field populations. Here, we artificially selected a colony of field-collected D. suzukii for resistance against spinosad and malathion. A quantitative genetic approach was then used to estimate realized heritability (h²) of resistance and predict the rates of resistance development. After 10 and 11 generations of selection, resistance to spinosad and malathion in D. suzukii females significantly increased by 7.55- and 2.23-fold, respectively. Based on the predicted rates of resistance development, assuming h² = 0.14 (mean h² of spinosad resistance in this study) and 90% of population was killed at each generation, 10-fold increase in LC₅₀ of D. suzukii females would be expected in nine generations for spinosad. However, 10-fold increase in LC₅₀ of D. suzukii females for malathion would be expected in 37 generations, assuming h² = 0.08 (mean h² of malathion resistance) and 90% of population was killed at each generation. These results indicate that the risk of resistance in D. suzukii populations exists against both spinosad and malathion. However, resistance would develop faster against spinosad as compared to malathion. Thus, resistance management strategies should be implemented proactively to maintain the effectiveness of these insecticides to control D. suzukii.

Susceptibility of Ixodes scapularis (Acari: Ixodidae) to Permethrin Under a Long-Term 4-Poster Deer Treatment Area on Shelter Island, NY

Pesticide resistance in medically significant disease vectors can negatively impact the efficacy of control efforts. Resistance research on ticks has focused primarily on species of veterinary significance that experience relatively high degrees of control pressure. Resistance in tick vectors of medical significance has received little attention, in part because area-wide pesticide applications are not used to control these generalist tick species. One of the few effective methods currently used for area-wide control of medically important ticks, including Ixodes scapularis Say (Acari: Ixodidae), is deployment of 4-poster devices. Deer self-apply a topical acaricide (permethrin) while feeding on corn from the devices. A 4-poster program using permethrin has been deployed on Shelter Island, NY to control I. scapularis populations since 2008. We collected engorged female ticks from deer in this management area and a location in the Mid-Hudson River Valley, NY without area-wide tick control. Larvae were reared from egg masses and their susceptibility to permethrin was tested. Larvae originating from a long-term laboratory colony were used as a susceptible baseline for comparison. Compared against the laboratory colony, resistance ratios at LC-50 for Shelter Island and Hudson Valley I. scapularis were 1.87 and 1.51, respectively. The susceptibilities of the field populations to permethrin were significantly lower than that of the colony ticks. We provide the first data using the larval packet test to establish baseline susceptibility for I. scapularis to permethrin along with information relevant to understanding resistance emergence in tick populations under sustained control pressure from 4-poster devices.

NEVBD Pesticide Resistance Monitoring Network: Establishing a Centralized Network to Increase Regional Capacity for Pesticide Resistance Detection and Monitoring

Pesticide resistance in arthropod vectors of disease agents is a growing issue globally. Despite the importance of resistance monitoring to inform mosquito control programs, no regional monitoring programs exist in the United States. The Northeastern Regional Center for Excellence in Vector-Borne Diseases (NEVBD) is a consortium of researchers and public health practitioners with a primary goal of supporting regional vector control activities. NEVBD initiated a pesticide resistance monitoring program to detect resistant mosquito populations throughout the northeastern United States. A regionwide survey was distributed to vector control agencies to determine needs and refine program development and in response, a specimen submission system was established, allowing agencies to submit Culex pipiens (L.) (Diptera:Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae) for pesticide resistance testing. NEVBD also established larvicide resistance diagnostics for Bacillus thuringiensis israelensis (Bti) and methoprene. Additional diagnostics were developed for Cx. pipiens resistance to Lysinibacillus sphaericus. We received 58 survey responses, representing at least one agency from each of the 13 northeastern U.S. states. Results indicated that larvicides were deployed more frequently than adulticides, but rarely paired with resistance monitoring. Over 18,000 mosquitoes were tested from six states. Widespread low-level (1 × LC-99) methoprene resistance was detected in Cx. pipiens, but not in Ae. albopictus. No resistance to Bti or L. sphaericus was detected. Resistance to pyrethroids was detected in many locations for both species. Our results highlight the need for increased pesticide resistance testing in the United States and we provide guidance for building a centralized pesticide resistance testing program.

Role of S180L polymorphism in etiology of malaria caused by Plasmodium falciparum in a small group of Pakistani population

The aim of our study was to investigate the role of S180L polymorphism in modulation of acquisition of malaria caused by Plasmodium falciparum in a small group of Pakistani population. A total of 133 individuals including 60 controls and 73 patients of malaria, caused by Plasmodium falciparum, were genotyped using allele-specific PCR. Ninety-two samples successfully demonstrated the PCR amplification results, while forty-one samples could not be genotyped due to failure in PCR amplification. The allele frequency for S180L polymorphism was deviant from Hardy-Weinberg equilibrium (HWE) of the population under observation. Association was found between the observed polymorphism and the occurrence of malaria caused by Plasmodium falciparum (p = 0.01). Chances of malaria caused by Plasmodium falciparum were low in CC genotype carriers in comparison to other genotypes (Odds ratio: 0.3016; 95% CI: 0.124-0.729). The present findings suggest that S180L polymorphism is important in modulating the probability of acquisition of malaria caused by Plasmodium falciparum in Pakistani population. The CC genotype plays a protective role in local population against this type of malaria.

Medical entomology--back to the future?

Some of problems and challenges facing Medical/Veterinary Entomology are presented from my perspective, focusing on the current millennium. Topics include anthropogenic environmental changes created by population growth, administrative problems hindering science's response to these changes, and some of the scientific discoveries potentially providing solutions. As the title implies, many recent research discoveries have yet to be translated into major changes in control approaches for the major vectorborne public health problems, thereby providing an interesting mix of modern surveillance technology used to track problems and direct historical intervention solutions.