Encephalomyelitis Associated with Akabane Virus Infection in Adult Cows

Abstract

Abstract. Between August and September 2000, five 2-7-year-old cows in Korea exhibited neurologic signs and were diagnosed as infected with Akabane virus based on the results of histopathology, immunohistochemistry, serology, and reverse transcription polymerase chain reaction (RT-PCR) analysis. Immunohistochemistry and RT-PCR were equally effective and sensitive for diagnosing Akabane virus infection during the early stage of infection. Typical lymphohistiocytic inflammation characterized by perivascular mononuclear cell infiltration, gliosis, neuronophagia, and neuronal loss was noted in the brain and the ventral horn gray matter of the spinal cord. The lesions in the brain were most prominent in the pons and medulla oblongata. Akabane virus antigen was detected in the brain and spinal cord, mainly in degenerating neurons and glial cells. RT-PCR analysis revealed a target band of expected size in four cows. This is the first report on an outbreak of natural Akabane virus infection in adult cattle.Key words: Akabane virus; cattle; immunohistochemistry; RT-PCR.Akabane disease (AD) is an arthropod-borne bunyaviral disease associated with abortion, stillbirth, and various congenital abnormalities in cattle, goats, and sheep. Akabane virus (AV) is a member of the Simbu group, genus Bunyavirus, family Bunyaviridae, and was first isolated from Aedes vexans and Culex triaeniorhynchus in 1960 and 1964, respectively, in Japan. 4,11 Sporadic outbreaks of AD have been reported in Japan, Taiwan, Australia, and Israel. 1,8,18 In Korea, the first AD outbreak was reported in 1980. 2 The pathogenesis of AV infection in cattle is well understood. Pregnant cows infected by AV through vectors generally do not develop any apparent clinical signs. However, during the early and mid to late gestation periods infection results in abortion and congenital arthrogryposis-hydranencephaly syndrome (AHS), respectively. 4,10 Although nonsuppurative encephalomyelitis may be observed in the late gestation infection in calves without AHS, encephalomyelitis induced by AV is unusual in cattle after birth. A few case of this condition caused by a highly virulent AV strain known as Iriki strain were reported in Japan and Taiwan, suggesting that AV may cause nonsuppurative inflammation in the brain and spinal cord of cows through horizontal rather than vertical transmission. 12,15 In July 1998, a severe outbreak of congenital abnormalities in calves was reported in most areas of Japan; a 5-month-old bull calf and 27 calves ranging from 1 to 27 days of age were examined, and their cases were diagnosed as AV infection. 19 Here, we describe an outbreak of natural AV infection in adult cows as revealed through histopathology, immunohistochemistry, neutralizing antibody assay, and reverse transcription polymerase chain reaction (RT-PCR) analysis.Between August and September 2000, 5 adult cows in Wonju City ranging from 2 to 7 years of age developed neurologic signs, including hypersensitivity, tremor, locomotor ataxia, or lameness. The cows were from fiv...

Diagnostic Survey of Bovine Abortion in Korea: With Special Emphasis on Neospora caninum.

“…Encephalomyeltis associated with Akabane virus infection was noted in adult cows between August and September 2000 [15]. While the outbreak subsided by the end of October 2000, a marked increase in the incidences of bovine abortion due to Akabane virus infection was observed during the fall of 2000 and early spring of 2001, which indicates a hematogenous spreading of virus from the infected dam to the fetuses.…”

The follow up study after massive outbreak of Akabane and bovine ephemeral fever viruses in Korea

“…These arthropod-borne viruses (arboviruses) are widely distributed from the tropical to temperate zones of the world and have been associated with hematophagous arthropod vectors such as Culicoides biting midges and mosquitoes. The particular vector species linked to the Akabane virus (AKAV) and bovine ephemeral fever virus (BEFV) are C. brebitarsis, C. oxystoma, C. nebuchlsus and C. nipponensis (Lee et al, 2002;Hsieh et al, 2005).…”

“…The S segment RNA contains nucleotides encoding two proteins, nucleoprotein (N) and nonstructural proteins (Elliott et al, 1990). Since the AKAV was first isolated in Japan in 1959, several Asian countries including Korea have reported outbreaks of AKAV infection in ruminant (Akashi et al, 1997;Bak et al, 1980;Lee et al, 2002;Liao et al, 1996;Nakajima et al, 1980). Therefore, there have been efforts to prevent Akabane disease with several kinds of vaccines in Korea (Kim et al, 2011).…”

Cleavage of Akabane virus S RNA in the brain of infected ruminants

“…It was shown that AKAV and, recently, also the Aino virus (AINV) [13,14] cause teratogenic malformations when susceptible pregnant ruminants are infected [15][16][17]. AKAV was identified, serologically or by virus isolation, in Japan, Korea, Taiwan, Israel, Turkey, and Australia [1,4,6,7,9,[16][17][18][19][20][21] The virion is enveloped and the genome consists of three segments of ss RNA of negative polarity. The small (S) segment RNA is 858 bases long and encodes two proteins: the nucleocapsid and non-structural proteins.…”