Meteorological factors affecting seroconversion of Akabane disease in sentinel calves in the subtropical Okinawa Islands of Japan

Tropical Animal Health and Production - Akabane virus, the pathogen-causing Akabane disease, is an arthropod-borne virus (arbovirus) transmitted by the Culicoides biting midge. A nationwide...     

Isolation and preliminary characterization of an orbivirus of the Palyam serogroup from biting midge Culicoides oxystoma in Japan

An orbivirus of the Palyam serogroup was isolated from Culicoides oxystoma collected in a cowshed in Kagoshima, Southern Kyushu Island, Japan. This is the first isolation of an orbivirus of the Palyam serogroup in Japan. The virus was a spherical non-enveloped RNA virus, approximately 60 nm in diameter. The virus was resistant to ethyl ether, sodium deoxycholate and freezing-thawing, but readily inactivated by trypsin. The virus was not stabilized by 1 M MgCl2, was labile at pH 3.0 and was not precipitated by protamine sulfate. Indirect immunofluorescent staining of infected Vero cells indicated the virus to be antigenically related to D'Aguilar and Bunyip Creek viruses of the Palyam serogroup. Neutralization tests showed the virus to have no relationship with D'Aguilar virus, but to have a one-way cross-reaction with Bunyip Creek virus. The virus was tentatively designated as Kagoshima virus. A serological survey indicated dissemination of the virus in cattle populations in Kagoshima Prefecture.     

ANTIBODIES TO AKABANE VIRUS IN AUSTRALIA

SUMMARY Neutralising antibody to Akabane virus was shown to develop in cattle in northern Australia throughout the year and also on the east coast of New South Wales in the summer during 1975/1976. Other species found to have antibody to Akabane virus were buffaloes, horses, camels and sheep, but no antibody was found in domestic chickens, ducks, wallabies or man. The biting midge Culicoides brevitarsis has been detected in all the major areas where antibody was demonstrated in this study.     

赤羽病研究进展

赤羽病是由阿卡班病毒引起牛、羊等动物流产、死产、死胎、胎儿畸形、以及先天性关节弯曲-积水性无脑综合征的一种虫媒传染病.20世纪30年代该病在澳大利亚羊群中首次暴发.近年来,我国许多省也流行本病,给畜牧业带来巨大损失.文章对该病的病原、流行病学、发病机理、抗原、诊断进行综述,为有效防控赤羽病提供参考.     

CONGENITAL BOVINE EPIZOOTIC ARTHROGRYPOSIS AND HYDRANENCEPHALY IN AUSTRALIA: Distribution of Antibodies to Akabane Virus in Australian Cattle after the 1974 Epizootic

At the end of the 1974 epizootic of bovine congenital arthrogryposis and hydranencephaly in south-eastern New South Wales, an Australia-wide serological survey (about 4,000 serums) was made to determine the ditribution of cattle possessing serum neutralising antibodies against Akabane virus. Eighty per cent of the serums from cattle in northern Australia (Western Australia, Northern Territory, and Queensland) were positive. A detailed study in the epizootic area in New South Wales (particularly around Bega) showed that 80 to 100% of serums from cows in herds in this area possessed neutralising antibodies. The animals possessing antibodies extended as far south as Genoa in north-eastern Victoria, and as far west as Darlington Point on the Murrumbidgee River. There were no positive herds along the Murray River, where an outbreak of the mosquito-borne disease Murray Valley encephalitis occurred in 1974. Serums tested from cows in the rest of Victoria, South Australia, south-western Western Australia, and Tasmania were negative. Arthrogrypotic calves born in Tasmania and south-western Western Australia were not associated with the presence of Akabane virus. In Papua New Guinea, serums collected from cattle at Boroka, Lae, and Goroka did not possess neutralising antibodies. The distribution of cattle possessing antibodies in Australia would fit a spread of the virus by Culicoides brevitarsis, a biting midge from which Akabane virus had been isolated on three occasions. The possibility of other vectors, as well as C. brevitarsis, was suggested by the presence of cows possessing antibodies at Alice Springs, where this biting midge has not been found. Possibly most cattle in northern Australia become infected early in life. The epizootics in New South Wales could occur when seasonal conditions allow a southerly extension of virus-infected C. brevitarsis which feed on susceptible pregnant animals. C. brevitarsis also bites sheep, and both neutralising antibodies to Akabane virus and congenitally deformed lambs have been observed in the epizootic area. An understanding of the distribtuion of Akabane virus and C. brevitarsis, a possible Australian vector for bluetongue virus, may prove useful if bluetongue should enter Australia.     

Culicoides: biological vectors of Akabane virus

Akabane virus replicated in Culicoides nubeculosus and Culicoides variipennis after intrathoracic inoculation and was maintained in both species of midge for at least 9 days post-infection. The virus also replicated to high concentration in C. variipennis after oral infection and was transmitted through a membrane by this species of midge 7-10 days after infection. The experiments described in this paper provided the first definitive evidence that Culicoides spp. are able to act as fully competent vectors of Akabane virus.     

Isolation of Chuzan virus, a new member of the Palyam subgroup of the genus Orbivirus, from cattle and Culicoides oxystoma in Japan

Five virus strains with identical antigenic properties were isolated from 3 RBC suspensions obtained from 2 healthy sentinel calves and from 2 pools of Culicoides oxystoma in cultures of a hamster lung cell line (HmLu-1). The virus was tentatively named Chuzan virus. The Chuzan virus was classified as a new member of the Palyam subgroup of the genus Orbivirus on the basis of its physicochemical, morphologic, and antigenic properties.     

ISOLATIONS OF AKABANE VIRUS FROM SENTINEL CATTLE AND CULICOIDES BREVITARSIS

SUMMARY A total of 14 isolations of Akabane virus were made from the blood of five cattle during sub-clinical infection. The serial isolation of this virus from four of these animals suggests a viraemia of at least 3 or 4 days. Neutralising antibody to Akabane virus in the serum of infected calves reached an initial peak titre of 32 to 256 four to five days after the viraemia but later rose further to a range of 64 to 512. Three isolations of Akabane virus were made from Culicoides brevitarsis collected nearby in the same period. C. brevitarsis was the dominant haematophagous midge present during that time. These findings strengthen the case for C. brevitarsis to be considered as a vector of Akabane virus.     

A SURVEY OF ANTIBODY TO AINO VIRUS IN CATTLE AND OTHER SPECIES IN AUSTRALIA

SUMMARY A serological survey of healthy cattle in Australia showed that antibodies to Aino virus were present in serums from cattle in northern Australia and down the east coast as far as central New South Wales in 1975, 1976 and 1977, but occurred with a lower frequency than antibodies to Akabane virus. in contrast to the findings with Akabane virus, no neutralising antibodies to Aino virus were detected in serums from camels, dogs or horses. Antibodies to both viruses were detected in buffaloes and sheep, but not in humans or any of the Australian indigenous species so far tested. All positive serums originated from within the known range of Culicoides brevitarsis.     

Phenology and attraction of potential Culicoides vectors of bluetongue virus in Basque Country (northern Spain)

Bluetongue virus is transmitted by Culicoides biting midges (Diptera: Ceratopogonidae). Culicoides associated with livestock were captured using CDC blacklight traps at three BTV-infected farms in Basque Country between November 2007 and December 2008. Twenty-seven and nineteen Culicoides species were collected in outdoor and indoor habitats respectively. Indoor insect community represented 86.1% of the whole captured individual biting midges. Culicoides obsoletus/Culicoides scoticus (two sibling species of the Obsoletus complex) were dominant throughout all months and sexes with maximum phenological peaks in November 2007 and June-July 2008. Culicoides lupicaris was the second most dominant species followed by Culicoides pulicaris (both species of the Pulicaris complex). Few specimens of Culicoides imicola, the principal Afro-Mediterranean vector of BTV, as well as four new species recorded for the Iberian Peninsula, were also collected. BTV was detected by RT-PCR from pools of C. obsoletus/C. scoticus, C. lupicaris and C. pulicaris parous females. DL-Lactic acid significantly attracted more C. obsoletus/C. scoticus females and males, C. lupicaris females, C. pulicaris females and Culicoides punctatus females and males; whereas acetone increased only the captures of Culicoides achrayi.     

Culicoides vectors of bluetongue virus in Chester Zoo

On four nights in June 2008, light traps were operated for Culicoides biting midges, the vector species for bluetongue virus (BTV), at five sites in Chester Zoo in north-west England. Over 35,000 Culicoides midges, of 25 species, were captured, including high densities inside animal enclosures. Over 94 per cent of all the Culicoides trapped were females of the Obsoletus group, which is implicated as the vector of BTV serotype 8 in northern Europe. The mean catch of this group per trap per night was over 1500, suggesting a potential risk of BTV transmission if the virus is introduced to Chester Zoo in the animals or midges in the summer.     

Genetic analysis of Akabane virus isolates from cattle in Korea

Bayesian Inference (BI) and Neighbor Joining (NJ) analyses of the phylogenetic relationships between the nucleotide sequences of the N gene of Akabane virus revealed an unclear topology among genogroups I–III, which was probably caused by genetic reassortment or recombination between these genogroups. In contrast, nucleotide and amino acid phylogenetic tree analyses of the M RNA segment agreed with the topologies obtained by using the BI and NJ methods. Therefore, distinct genogrouping of Akabane virus isolates should be performed using the M RNA segment. Four Korea isolates were classified into genogroup II together with Akabane virus strains isolated from all areas of Japan, including Okinawa Island. However, more nationwide isolates and more clinical data from Korean cattle farms will be required in the future to confirm the precise relationships between genotypes and pathogenicity.     

Seasonal dynamics of biting midges (Diptera: Ceratopogonidae: Culicoides), the potential vectors of bluetongue virus, in Sweden

The outbreak of bluetongue (BT) in northern Europe 2006 initiated the monitoring of vectors, biting midges of the genus Culicoides in Sweden. In order to determine the diversity, distribution and seasonal dynamics of Culicoides, weekly collections were made during 2008 and during March-December 2009 using the Ondestepoort Veterinary Institute black light trap. Twenty sampling sites were selected in 12 provinces. In total of 30,704 Culicoides were collected in 2008 and 32,252 in 2009. The most abundant species were the potential vectors of BTV Culicoides obsoletus/C. scoticus that comprised of 77% of the total catches. Other biting midges collected were Culicoides impunctatus (9%), Culicoides grisescens (3%), Culicoides punctatus (2%), Culicoides chiopterus (2%) and Culicoides pulicaris (2%). Culicoides obsoletus/C. scoticus were most abundant during May-June and August-September. The majority of the species were active from March to November in 2008 and April to October in 2009. Species considered as potential vectors of bluetongue virus (BTV) occurred as far north as latitude 65°N (Kalix).     

Bluetongue and epizootic hemorrhagic disease virus isolation from vertebrate and invertebrate hosts at a common geographic site

One serotype of bluetongue virus (BTV) and two serotypes of epizootic hemorrhagic disease virus (EHDV) were isolated from vertebrate and invertebrate hosts on a farm in Colorado. The isolations were from blood samples collected a week apart from a dairy heifer with stomatitis and laminitis; EHDV serotypes 1 and 2 were isolated from the first blood sample, and BTV serotype 13 and EHDV serotype 1 were isolated from the second. Antibodies to EHDV and BTV were detected in the serum from this heifer. Both EHDV serotypes and BTV serotype 13 were isolated from pools of female biting gnats (Culicoides variipennis) that had not had a recent blood meal. The BTV insect isolate was biologically transmitted by female gnats from an infected donor sheep to a recipient host sheep. Culicoides variipennis was the predominant insect collected during three nights of light trap captures at the farm.     

Encephalitis of cattle caused by Iriki isolate, a new strain belonging to Akabane virus

A disease characterized by nervous signs was found in 10 calves in two districts in Kagoshima Prefecture, Japan, from October to November, 1984. Histopathological changes of nonpurulent encephalitis were found in every case. An agent, named Iriki isolate, was isolated from the cerebellum of a calf in HmLu-1 cell cultures. All of the affected calves possessed neutralizing antibody to the virus. A high seropositive rate to the virus in cohabiting cattle and cattle kept in the epizootic area, and seroconversion to the virus in 1984, were disclosed. Experimental infection of calves with Iriki isolate produced severe nervous signs and histopathological changes similar to those of the natural infection. These seroepidemiological findings and animal experiments established that Iriki isolate is the causative agent of the disease. Iriki isolate was considered as a variant of Akabane virus since the virus showed cross reaction with Akabane virus in virus neutralization tests.     

Viruses isolated from Culicoides midges in South Africa during unsuccessful attempts to isolate bovine ephemeral fever virus

Five viruses, unrelated to bovine ephemeral fever virus (BEFV), were isolated from Culicoides biting-midges collected during the summer months of the years 1968-69 and 1969-70 near a cattle herd in which cases of BEF occurred and at an open horse stable at Onderstepoort. These viruses were investigated by means of serological, electron-microscopical and physicochemical tests. It was established that 2 isolates, Cul. 1/69 and Cul. 2/69, were related to each other and belonged to the Palyam subgroup of the genus Orbivirus, that isolate Cul. 3/69 belonged to the equine encephalosis subgroup of the genus Orbivirus, while Cul. 1/70 was related to Akabane virus, which belongs to the Simbu subgroup of the family Bunyaviridae. One isolate, Cul. 5/69, though prevalent in the cattle population, could not be identified at this point. A brief serological survey indicated that the cattle in the nearby herd possessed antibodies against all the isolates except Cul. 3/69. BEFV could not be isolated in mice or in cultured cells from the wild-caught Culicoides.     

Detection of Culicoides brevitarsis activity in Kyushu

Culicoides brevitarsis transmits important ruminant arboviruses, such as Akabane, Aino and bluetongue viruses. The presence of this species has so far been recognized primarily in Okinawa, the southernmost prefecture of Japan. In entomological surveys in 2008 and 2009, C. brevitarsis was collected at 8 sites throughout Nagasaki, Kumamoto and Kagoshima Prefectures. The collection sites are all located near pastures, where the larvae of C. brevitarsis can grow in cattle dung left in the field. C. brevitarsis was confirmed at the same sites in two consecutive years, suggesting that it overwinters in Kyushu. Given the risk of arbovirus transmission, the ecology of C. brevitarsis in Japan, such as its distribution range, seasonal abundance and larval breeding sites, should be investigated in more detail.     

Studies on the pathogenesis of bovine ephemeral fever in sentinel cattle. I. Virology and serology

Twenty-two sentinel cattle were observed daily during an outbreak of ephemeral fever on a dairy farm in eastern Australia in the summer of 1981–192. Of the 22 cattle, 9 developed clinical ephemeral fever. None developed sub-clinical infection. The pattern of the epidemic was a single index case followed 10 days later by the main epidemic wave which lasted for 7 days. This wave stopped when there were still 14 uninfected susceptible animals remaining in the sentinel group, and when biting flies were very active. Ten isolations of bovine ephemeral fever virus were made in Aedes albopictus tissue cultures from the blood of 5 clinical cases. One hundred and twelve isolations of CSIRO Village virus and one each of Kimberley and Akabane viruses were also made from various members of the sentinel group. There was serological evidence that infections with Tibrogargan, Tinaroo and Aino viruses also occurred in 6 cattle in the observation period. The 13 cattle undergoing a sub-clinical viraemia with CSIRO Village virus, Tibrogargan, Kimberley, Akabane or Aino viruses at the time of the main outbreak, appeared to be temporarily protected against ephemeral fever. However, 9 of the 11 still remaining in the herd were susceptible in a subsequent outbreak of ephemeral fever 2 years later. Evidence is presented that subclinical infections with other arboviruses may limit an ephemeral fever epidemic by providing temporary protection by interference.     

A mass attack by the biting midge culicoides nubeculosus (Mg.) (Dipteria, Ceratopogonidae) on grazing cattle in Denmark. A new aspect of sewage discharge.

A consequence of sewage discharge into a shallow marsh pool was large-scale hatching of the biting midge Culicoides nubeculosus from the recipient and mass attacks by this blood-sucking insect on grazing cattle. Culicoides nubeculosus is a great nuisance due to the painful bite and in Denmark it is a potential vector of pathogenic agents. In the future, these aspects of sewage discharge must be borne in mind.