Diagnostic and epidemiologic analysis of the 2008-2010 investigation of a multi-year outbreak of contagious equine metritis in the United States.

Contagious equine metritis (CEM) is a highly contagious venereal disease of horses caused by Taylorella equigenitalis. During testing for semen export purposes, a stallion in Kentucky was found to be T. equigenitalis culture positive in December of 2008. This finding triggered an extensive regulatory investigation to search for additional positive horses, determine the extent of the outbreak, identify the potential source of the outbreak, and ultimately return the United States to CEM-free status. The investigation included over 1000 horses located in 48 states. Diagnostic testing found a total of 22 stallions, 1 gelding and 5 mares culture positive for T. equigenitalis. Epidemiologic analysis indicated that all of the positive horses were linked to a single common source, most likely a Fjord stallion imported into the United States in 2000. The T. equigenitalis strain subsequently spread to other stallions via undetermined indirect mechanisms at shared breeding facilities, and to mares via artificial insemination and live breeding. This CEM outbreak and investigation represent the largest ever in the United States based on the number of exposed horses tested and their geographic distribution.

Endemic human mosquito-borne disease in Wisconsin residents, 2002-2006.

INTRODUCTION: West Nile virus (WNV) and La Crosse virus (LAC) are the primary mosquito-borne arboviruses associated with human disease in Wisconsin. We examined WNV and LAC human illness surveillance data collected during 2002 through 2006. METHODS: ELISA-based tests developed by the Centers for Disease Control and Prevention (CDC) were used to detect acute WNV and LAC infection in patient sera or cerebral spinal fluid. Public health personnel conducted patient follow-up using standard arbovirus reporting forms. CDC/Council of State and Territorial Epidemiologists definitions were used to determine cases. RESULTS: From 2002 through 2006, 114 confirmed human cases of WNV illness were reported in Wisconsin residents; 82% of illness onsets occurred during August or September. Median age of WNV case patients was 51 years, 49% reported neuroinvasive disease, 56% were hospitalized, and 7 cases were fatal. Confirmed LAC illnesses declined from a high of 27 cases during 2003 to a low of 3 cases during 2005 and 2006. Most LAC illnesses occurred in residents of Western Wisconsin; median age of LAC cases was 9 years. Mean annual incidences of reported confirmed WNV illnesses calculated for high, medium, and low population density groupings were very similar (range: 0.40-0.46 cases/100,000 population). CONCLUSIONS: Humans are at risk for mosquito-borne diseases in Wisconsin. Protection and prevention measures are important statewide, especially during July through September when the risk is greatest.

DNA vaccination of the American crow (Corvus brachyrhynchos) provides partial protection against lethal challenge with West Nile virus.

The New York 1999 strain of West Nile virus (WNV) is nearly 100% fatal in the American crow (Corvus brachyrhynchos). We evaluated four WNV vaccine formulations in American crows, including intramuscular (i.m.) DNA vaccine, i.m. DNA vaccine with adjuvant, orally administered microencapsulated DNA vaccine, and i.m. killed vaccine. Neutralizing antibodies developed in approximately 80% of crows that received the DNA vaccine i.m. (with or without adjuvant), and in 44% that received the killed vaccine. However, no crows that received the oral microencapsulated DNA vaccine or the placebo developed WNV antibodies. All crows were challenged 10 wk after initial vaccination. No unvaccinated crows survived challenge, and survival rates were 44% (i.m. DNA vaccine), 60% (i.m. DNA vaccine with adjuvant), 0% (oral microencapsulated DNA vaccine), and 11% (killed vaccine). Peak viremia titers in the birds that survived were significantly lower as compared to titers in birds that died. Parenteral administration of a WNV DNA vaccine was associated with reduced mortality but did not provide sterile immunity.

West Nile virus quantification in feces of experimentally infected American and fish crows.

To better understand the potential environmental health risk presented by West Nile virus (WNV)-contaminated feces, we quantified the amount of WNV present in the feces of experimentally infected American crows (Corvus brachyrhynchos) and fish crows (Corvus ossifragus). Peak fecal titers ranged from 10(3.5) to 10(8.8) plaque-forming units (PFU)/g for 10 American crows and from 10(2.3) to 10(6.4) PFU/g for 10 fish crows. The presence of infectious WNV in bird feces indicates a potential for direct transmission of WNV. Thus, handlers of sick or dead birds should take appropriate precautions to avoid exposure to fecal material.