Vectors and Pathogens

Topics: Tick, Dermacentor variabilis, Argasidae Pages: 4 (1015 words) Published: October 20, 2014
BHS432 Module 2 – Case Assignment:
Vectors and Pathogens
Spring 2013

Question 1a:
Describe differentiating characteristics between Dermacentor variabilis, Ixodes pacificus, and Ornithodoros hermsi ticks. Question 1b:
Identify vectorborne diseases associated with these ticks, and describe the pathogens associated with these diseases. Question 1c:
Describe preferred feeding locations of ticks.  
Question 2:
Describe the effect of climate on vectors and vectorborne diseases.

The western-blacklegged tick (Ixodes pacificus) can transmit the organisms responsible for causing anaplasmosis and Lyme disease in humans. Wild rodents and other mammals are likely reservoirs of these pathogens. This tick is distributed along the Pacific coast of the United States. ” Larvae and nymphs feed on birds and small rodents, while adult ticks feed on deer and other mammals” (J. BURRASCANO, 1988). Adult ticks are primarily associated with pathogen transmission to humans. Ornithodoros hermsi are called “soft” ticks because they have a soft outer covering Argasid ticks have multiple life stages. Each life stage may feed several times, for only minutes at a time. Most patients rarely every see or know they have been bitten by a soft tick. Primary vector of Rocky Mountain Spotted Fever (RMSF) in southeastern states. Adult tick preferred host: large and medium-sized mammals including domestic dog. “Often bites humans. Immature stages preferred host: small rodents” (K. Clark, 2004).

Dermacentor variabilis, also known as the American dog tick or wood tick, is found predominantly in the United States, east of the Rocky Mountains and as its name suggests, and is most commonly found on dogs as an adult. The tick also occurs in certain areas of Canada, Mexico and the Pacific Northwest of the U.S.. Dermacentor variabilis is a 3-host tick, targeting smaller mammals as a larva and nymph and larger mammals as an adult. “Although it is normally found on dogs, this tick will readily...


References: J. BURRASCANO, 1988 http://www.lymenet.org/BurrGuide200810.pdf Retrieved on
24 January 2013
K. Clark, 2004 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC525154/ Retrieved on
24 January 2013
http://www.stlmosquitocontrol.com/ticks/type-of-ticks/ Retrieved on 24 January 2013
VCA Animal Hospitals, 2011 http://www.vcahospitals.com/main/pet-health-
information/article/animal-health/ticks-in-dogs/725 Retrieved on 24 January 2013
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