Investigations into the vector competency of arthropods for two Ehrlichias: Ehrlichia risticii and Cowdria ruminantium

Three studies relating to the vector competency of several species of ticks and <i>Simulium</i> spp. (blackflies) for <i>Ehrlichia risticii</i>, causative agent of Potomac horse fever (PHF) and <i>Amblyomma variegatum</i> for <i>Cowdria ruminantium</i>, causative agent of heartwater, are described. <i>Dermacentor variabilis, Rhipicephalus sanguineus, Amblyomma americanum and Ixodes scapularis</i> ticks were investigated for their ability to acquire and transmit PHF. Larval and nymphal ticks were exposed to <i>E. risticii</i> by feeding on mice inoculated with the organism. Molted exposed ticks were then allowed to feed on susceptible ponies or mice and were examined by light and electron microscopy. No evidence of transmission, either clinically or by seroconversion in mice or ponies was observed. Blackflies (<i>Simulium</i> spp.) were trapped in an area endemic for PHF and inoculated into mice in an attempt to demonstrate <i>I. risticii</i>. No evidence of seroconversion by mice to <i>E. risticii</i> was observed. Two laboratory colonies of <i>Amblyomma variegatum</i> ticks were investigated for their ability to acquire and transmit C. <i>ruminantium</i> and was febrile. Nymphs from both laboratory groups were simultaneously fed on a goat that had been infected with C. <i>ruminantium</i> and was febrile. Engorged nymphs from both groups were replete from feeding on three consecutive days. Nymphs from both groups were then incubated under identical conditions until molting.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Veterinary Medical Sciences

Department dc:contributor.department

Veterinary Medical Sciences

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1990

Author dc:creator

• Hahn, Nina

Chair dc:contributor.committeechair

• Zajac, Anne M.

Committee members dc:contributor.committeemember

• Schurig, Gerhardt G.
• Perry, Brian D.
• Sonenshine, Daniel
• Kocan, Katherine M.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-09202005-090950

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/39407