Date of Graduation

5-2021

Document Type

Thesis

Degree Name

Master of Science in Entomology (MS)

Degree Level

Graduate

Department

Entomology and Plant Pathology

Advisor/Mentor

Loftin, Kelly M.

Committee Member

Szalanski, Allen L.

Second Committee Member

Steinkraus, Donald C.

Keywords

Entomology; Feral hogs; Ixodidae; Rickettsia; Tick-borne pathogens

Abstract

Feral hogs (Sus scrofa L.) are an invasive species throughout the southeast United States and found in every Arkansas county. As feral hogs invade new habitat, they can disrupt ecosystems, damage agriculture systems, and bring ticks and tick-borne pathogens with them. There are no surveys of the tick species parasitizing the Arkansas feral hog populations or the pathogens they carry. This is a public health concern because feral hogs occupy often same geographical regions as humans and livestock and can harbor over 45 animal diseases and parasites. The ticks carried by feral hogs can carry tick-borne pathogens that can cause diseases such as Ehrlichiosis, Rocky Mountain spotted fever and Lyme disease.

In this study, tick collections were taken from feral hogs trapped by Arkansas Game and Fish Commission, USDA APHIS Wildlife Services and University of Arkansas Cooperative Extension Service personnel for control purposes on private properties. From February 2019 to January 2020, 220 feral hogs were sampled for ticks in 11 Arkansas counties. Of the 3,009 ticks that were collected, 95.4% of them were Amblyomma americanum (L.), 2.4% were Dermacentor variabilis (Say), 0.6% were Amblyomma maculatum (Koch), and 0.3% were Ixodes scapularis (L.). Tick loads on the hogs ranged from 0-96. Most of the sampled hogs had single species infestations with 132 or 138 of these hogs being infested only A. americanum ticks. The remaining single species infestations were four hogs infested with I. scapularis and two with D. variabilis. Dual species infestations were seen on 42 hogs with 37 of these being infested with A. americanum and D. variabilis, four with A. americanum and A. maculatum and one with A. americanum and I. scapularis.

The ticks collected from the feral hogs were also used to test for pathogens. Pooled DNA extractions and PCR were used to survey the prevalence of Rickettsia, Ehrlichia and Borrelia bacteria found in the ticks. Each pooled DNA extractions contained 1-10 ticks of the same host, species, life stage, and sex. From the DNA extractions used in this survey 75 were A. americanum, nine were D. variabilis and one was A. maculatum. PCR primers used targeted the citrate synthesis gene in Rickettsia, 16S gene in Ehrlichia and flab gene in Borrelia. Results from the PCR were 24 Rickettsia positives samples from 23 A. americanum pools and one D. variabilis pool. Five of the Rickettsia positives samples from A. americanum pools were purified, sequenced, and found to be a 100% match to Rickettsia amblyommatis. No Borrelia or Ehrlichia species were found in this survey. However, that does not mean that they are no present in the Arkansas feral hog populations as the hogs were found to host the tick species that carry those pathogens.

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