• Document: BORNE BY BUGS, DISEASES OF CONCERN. Heartland Virus
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BORNE BY BUGS, DISEASES OF CONCERN Steven R. Bolin, DVM, MS, PhD Department of Pathobiology and Diagnostic Investigation College of Veterinary Medicine Diagnostic Center for Population and Animal Health, Rm 265 Michigan State University Lansing, MI 48910 Heartland Virus In June of 2009, a new disease appeared in northwestern Missouri that affected two farmers living 60 miles apart. Both men had removed ticks from their bodies shortly before they developed fever, fatigue, anorexia, and non-bloody diarrhea. On admission to the hospital, both men showed low white bold cell count, low platelet count, and elevated liver aminotransferases. Antibiotic therapy was administered and samples of blood were sent to the CDC to test for known tick borne pathogens, and for unknown agents. After several days in the hospital, both men were discharged. Fatigue and anorexia lasted for weeks after discharge and both men suffered short term memory loss. Laboratory testing at the CDC resulted in the isolation of a virus. Further testing of viral infected cell cultures using electron microscopy showed an enveloped virus morphologically similar with viruses in the Bunyaviridae family. Using molecular techniques, the nucleic acid sequence of the viruses from both men were derived and found to be highly similar to each other. The virus was classified as a phlebovirus and genetic analyses showed that the virus was most closely related to the newly identified Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV). The SFTSV is considered the cause of a new disease of people in rural areas of China. The new virus isolated from the farmers in Missouri was termed Heartland virus (HRTV). When comparisons were made, it was found that the disease induced by HRTV and the disease induced by SFTSV were similar. Both diseases occurred in farmers or people living in rural areas, most of the affected people were over 50, ticks bites were a common factor, the affected people presented with signs and symptoms of fever, fatigue, anorexia, leukopenia, thrombocytopenia, and gastrointestinal signs. The mortality rate associated with SFTSV in China was 30%. The likely source of SFTSV in China was ticks, which were shown to carry the virus. Thus, it was speculated that the source of HRTV also was ticks and the most common tick in northwestern Missouri is Amblyomma americanum (A.a.), the lone star tick. Since those first 2 cases of HRTV infection in 2009, at least 7 additional cases have occurred. Missouri has had five more confirmed cases of HRTV infection that were non-fatal and there have been single fatal cases reported from Tennessee and Oklahoma. In 2012, ticks were collected by drag, baited traps, or removal from animals in Missouri at the farms owned by the first two men infected with HRTV and at 10 other sites in the general area of the farms. Over 56,000 ticks were collected in April, June, and August. Included in the collection were 1,987 adults, 7,271 nymphs, and 45,760 larvae that were A.a.; 1,385 adults, 12 nymphs, and 6 larvae that were Dermacentor variabilis; and only 7 Ixodes dentatus ticks. The HRTV was detected only in A.a nymphs that had been collected at 2 of 12 total sites. Thus, the HRTV was found in A.a. ticks, as had been speculated after the first two cases of disease were described. To date, a potential reservoir host has not been identified. A serologic survey for antibody that might be induced by HRTV, or by an unknown similar virus, was performed using convenience samples of serum collected from farmed animals that were located in 29 counties in Minnesota. The laboratory test used was an ELISA manufactured in China for detection of antibody against the SFTVS nucleoprotein. It was assumed that since HRTV and SFTVS were genetically similar, that ELISA would detect antibody raised against HRTV or some other closely related phlebovirus. The ELISA identified 64 of 414 cattle, 10 of 92 goats, 6 of 48 sheep, 35 of 296 white-tailed deer, and 7 of 39 elk located in 24 of 29 counties with antibody against the SFTVS nucleoprotein. Chikungunya virus Chikungunya virus (CHIKV) is in the Semliki Forrest Virus complex of alphaviruses within the Togaviridae family of viruses. Three genetic cluster of CHIKV are recognized: Asian, West African, and Central/South/East African. CHIKV is responsible for periodic outbreaks of disease in Africa, in islands in the Indian Ocean, and in Southeast Asia. Signs and symptoms of disease begin about 3 to 7 days after being bitten by an Aedes mosquito that carries CHIKV. The disease commonly presents as fever accompanied by severe joint pain, often in the hands and feet. Headache, muscle pain, joint swelling, or rash also may occur. In most cases, the disease lasts about a week, but long term joint pain may occur in some people. Severe disease is seen in newborns, elderly, and people with existing chronic disease. A map of the distribution CHIKV in 2006 showed the virus in sub Saharan Africa, in countries and isl

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