Heartwater: Risk to US Livestock and Wildlife

Christopher Hensley and Pete D. TeelSenior Forensic and Investigative Sciences & Psychology Double Major, 2012

And Professor and Associate Department HeadDepartment of Entomology

Texas A&M University

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Overview

• General Information• Issue & Threat• Cattle Egret• Geographic Distribution• Impact• Conclusions

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Heartwater: General Information

• African tick borne diseaseAffects ruminants (broad range of species)Not in US, but in Caribbean

• PathogenEhrlichia ruminantium

(Formerly Cowdria)

• Tick VectorsGenus Amblyomma

(12 species recognized)

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Genus Amblyomma

• A. variegatum• Tropical Bont Tick• Spread to 14 Caribbean Islands

Other principle African vector species not in Western Hemisphere• A. hebraeum• A. gemma

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Issue & Threat

• Risk of Heartwater to North America• Presence of primary vector and pathogen in Caribbean

• Discovery of native tick to be efficient experimental vector

• Role of cattle egrets as host and transport of

immature ticks

• Supportive climate

• Diversity of livestock andWildlife hosts in US

Potential Native Tick Vector

• The Gulf Coast tick, Amblyomma maculatum• Laboratory studies using a goat – tick model• Findings show A. maculatum very capable of

acquiring E. ruminantium from sub-clinical, infected goats. (See Mahan et al. 2000)

• Summation: A substantial risk as vector.• Vector capacity under field conditions not yet

tested.

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Cattle Egret: Host & Transport

• Caribbean introductions1940-50’s• Now widespread in Western

Hemisphere• Nest throughout Caribbean• Host to immature Amblyomma ticks

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Cattle Egret: Migratory Risk

• Migrate across Americas• Involved in inter-island travel• Caribbean birds found in Florida Keys

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Geographic Distribution

• Heartwater and Amblyomma vectors are widespread in Africa south of the Sahara

• Caribbean introduction and spread– First reported 1830s (limited to 3 islands)– Tick expansion 1970s-1980s to 14 islands

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Geographic Distribution

• Potential spread – North and South American mainlands

• Southeastern US at high risk– Close proximity– Suitable climate– Livestock density– Native and Exotic deer

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Impact

• Highly fatal• Economic risks

– high cost for containment and elimination• No drugs or vaccines• Surveillance testing• Quarantine

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Conclusions

•Vigilance to changes in Caribbean•Support efforts to Caribbean containment•Active surveillance of ticks from Texas to Florida and Georgia into National Tick Surveillance Program (USDA, APHIS, VS)•Contingency response at state & federal levels •Educate owners and veterinary professionals

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Resources Available

http://www.anapsid.org/heartwater.html http://www.avianweb.com/cattleegrets.html http://www.cfsph.iastate.edu/DiseaseInfo/disease.php?name=heartwater http://www.cfsph.iastate.edu/DiseaseInfo/factsheets.php http://www.epi.ufl.edu/?q=node/34 http://www.uniprot.org/taxonomy/34610 http://www.vetmed.ucdavis.edu/vetext/INF-DA/INF-DA_HEARTWATER.HTML