Location: Livestock Arthropod Pest Research Unit
2022 Annual Report
Objectives
Objective 1: Determine parameters such as tick range, movement and suitable habitats, to produce models of the risk of tick-borne disease outbreaks, and potential for introduction of invasive ticks in response to climate change and other perturbations.
Objective 2: Develop methods to prevent, eradicate and control introduction of exotic ticks.
Approach
Ticks are a major threat to the livestock industry and human health. Other than cattle fever ticks, Rhipicephalus (Boophilus) microplus and R. annulatus, threats to livestock by high-consequence foreign pests are always present and one example of this is the recent discovery of the Asian longhorned tick, Haemaphysalis longicornis in seventeen states with an eastern boundary from Rhode Island south to North Carolina and a western boundary from Missouri south to Arkansas. There are other potentially invasive tick vectors (e.g., Amblyomma variegatum, Hyalomma spp., Rhipicephalus appendiculatus) and species that are expanding their ranges within the United States (e.g., A. americanum, A. maculatum, A. mixtum). Likewise, there are high-consequence foreign tick-borne pathogens, like African swine fever, that could devastate U.S. animal agriculture if their emergence involved transmission by native tick species.
The research addresses the following research components in the 2019-2024 Veterinary, Medical, and Urban Entomology National Program (NP 104) Action Plan: Component 1: Veterinary Entomology, Problem Statement 1A Improved Integrated Pest Management of Ticks of Veterinary Importance and Component 2: Medical Entomology, Problem Statement 2D Improved Surveillance and Control of Ticks of Medical Importance. This research addresses ARS Performance Measure for Goal 4.3: Provide scientific information to protect animals, humans, and property from the negative effects of pests and infectious diseases. Develop and transfer tools to the agricultural community, commercial partners, and government agencies to control or eradicate domestic and exotic diseases and pests that affect animal and human health.
Progress Report
Project #3094-32000-044-000D, Management of Ticks of Veterinary Importance, is a new project beginning in fiscal year (FY) 22 as the result of a realignment Program Direction and Resource Allocation Memo (Nov. 2021). The two objectives in this project were transferred to this project from Project #3094-32000-042-000D, Integrated Pest Management of Cattle Fever Ticks, which has had critical vacancies since FY20.
In support of Objective 1, to determine variables that influence tick range, suitable tick habitats, risk of tick-borne disease outbreaks, and potential for introduction of invasive ticks, field experiments were conducted and completed in south Texas to further clarify the relationship between soil salinity and the survival rate of ixodid tick eggs. Factors like humidity and soil moisture content appear to impact survival of tick eggs on or near coastal soils. Additionally, paired field-testing sites were set up to determine if the presence of invasive Guinea grass impacts predation of fallen engorged female ticks. However, drought conditions in south Texas have slowed predation studies with engorged female ticks.
In support of Objective 2, determine genetic differences between H. longicornis populations from the United States and its native and invaded range through comparative molecular studies, complete mitochondrial haplotypes from fifty-seven North American and East Asian H. longicornis isolates were acquired and sequenced. The genomes were amplified using multiple long-range polymerase chain reaction and used to construct Illumina shotgun sequencing libraries. Since these data were generated, additional samples from U.S. collaborators including multiple county and state records (e.g., Kentucky, Ohio, Mchigan, South Carolina) have been added. These new samples provide important information about detection and range expansion of H. longicornis.
Accomplishments
Review Publications
Showler, A., Saelao, P. 2022. Integrative alternative tactics for ixodid control. Insects. https://doi.org/10.3390/insects13030302.
Bajwa, W.I., Tsynman, L., Egizi, A.M., Tokarz, R., Maestas, L.P., Fonseca, D.M. 2022. The Gulf Coast tick, Amblyomma maculatum (Ixodida: Ixodidae) and spotted fever group Rickettsia in the highly urbanized northeastern US. Journal of Medical Entomology. https://doi.org/10.1093/jme/tjac053.
