Viral neurotropism, peripheral neuropathy and other morphological abnormalities in bovine ephemeral fever virus-infected downer cattle.

OBJECTIVE: This study assessed the neurotropism of bovine ephemeral fever (BEF) virus (BEFV) and described histomorphological abnormalities of the brain, spinal cord and peripheral nerves that may causally contribute to paresis or paralysis in BEF. METHODS: Four paralysed and six asymptomatic but virus-infected cattle were monitored, and blood and serum samples screened by qRT-PCR, virus isolation and neutralisation tests. Fresh brain, spinal cord, peripheral nerve and other tissues were qRT-PCR-tested for viral RNA, while formalin-fixed specimens were processed routinely and immunohistochemically evaluated for histomorphological abnormalities and viral antigen distribution, respectively. RESULTS: The neurotropism of BEFV was immunohistochemically confirmed in the brain and peripheral nerves and peripheral neuropathy was demonstrated in three paralysed but not the six aneurological but virus-infected animals. Wallerian degeneration (WD) was present in the ventral funicular white matter of the lumbar spinal cord of a paralysed steer and in cervical and thoracic spinal cord segments of three paralysed animals. Although no spinal cord lesions were seen in the steer euthanased within 7 days of illness, peripheral neuropathy was present and more severe in nerves of the brachial plexuses than in the gluteal or fibular nerves. The only steer with WD in the lumbar spinal cord also showed intrahistiocytic cell viral antigen that was spatially distributed within areas of moderate brain stem encephalitis. CONCLUSION: The data confirmed neurotropism of BEFV in cattle and documented histomorphological abnormalities in peripheral nerves and brain which, together with spinal cord lesions, may contribute to chronic paralysis in BEFV-infected downer cattle.

Varicella, ephemeral breastfeeding and eczema as risk factors for multiple sclerosis in Mexicans.

OBJECTIVE: It has been suggested that the incidence of multiple sclerosis (MS) in Mexico and other countries of Latin America has increased steadily for the last two decades. We made a thorough search of antecedents on MS patients that could be potential risk factors. METHODS: A case-control study was conducted using a questionnaire that included demographic, nutritional, infectious and personal antecedents previously identified in other reports as possible risk factors for MS. RESULTS: The frequency of varicella, ephemeral breastfeeding and eczema in the medical history of MS patients were significant when compared with controls; all appeared to be mutually additive. However, they were unrelated with clinical characteristics or disease severity. CONCLUSION: During the last decades, breastfeeding has been abandoned in large segments of society and the incidence of varicella and childhood eczema keeps a north-south gradient similar to that described for MS. These factors may participate in the sharp increase of MS in countries like Mexico traditionally considered as an area of very low incidence.

Evaluation of the effect of ketoprofen on experimentally induced ephemeral fever in dairy heifers.

OBJECTIVE: To evaluate ketoprofen for the therapy of ephemeral fever. DESIGN: A blind controlled clinical trial. ANIMALS: Sixteen cattle (one immature Holstein bull, eight Holstein and seven Jersey heifers). PROCEDURE: Ephemeral fever was induced by the intravenous injection of blood leucocyte layer from a clinical case. Ketoprofen solution or a coded placebo was injected intramuscularly at the rate of 3 mg/kg daily for three days. RESULTS: Ketoprofen reversed locomotor dysfunctions significantly compared with controls, but did not have any effect on rectal temperatures, leucocyte counts, plasma fibrinogen concentrations, ionised Ca-concentrations or the presence of dyspnoea. CONCLUSION: Ketoprofen is a safe and effective drug for the treatment of locomotor symptoms of milk fever, but has no effect on the duration of clinical respiratory abnormalities.

Demonstration of vascular permeability changes in cattle infected with bovine ephemeral fever virus.

Five cattle infected with bovine ephemeral fever virus were necropsied on the day after onset of clinical disease, when clinical signs of lameness were most severe. Gross lesions observed included a serofibrinous polyserositis involving the synovial, pericardial, thoracic and abdominal cavities. The associated histological changes consisted primarily of oedema and an influx of neutrophils into affected tissues and fluids. In a further eight infected cattle, increases in permeability of vessels associated with serosal surfaces were demonstrated by labelling with either colloidal carbon or Evans blue. Intravenous injections of carbon provided both macroscopic and histological labelling of affected vessels. Evans blue appeared to be more sensitive than carbon but did not provide a histological marker of vascular permeability and provided labelling of tissues rather than individual vessels. The main sites of increased permeability were synovial, pericardial, thoracic and abdominal serosae.

The relationship between selenium deficiency and the development of pulmonary and subcutaneous emphysema in bovine ephemeral fever virus-infected cattle.

Bovine ephemeral fever (BEF) was diagnosed on several commercial farms around Harare, Zimbabwe. The affected animals showed signs of fever (40-41.5 degrees C), depression, ruminal stasis, lameness and recumbency. Eight of those attended had severe respiratory distress and subcutaneous emphysema. Haematological and biochemical results indicated leukocytosis with an attending lymphopaenia. Selenium deficiency was detected only in those animals which showed respiratory embarrassment and subcutaneous emphysema.

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 1981-82. 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.

Subcutaneous and pulmonary emphysema as complications of bovine ephemeral fever.

Subcutaneous and pulmonary emphysema was observed in some cattle on farms on which outbreaks of bovine ephemeral fever (BEF) occurred. BEF virus was isolated in baby hamsters from one of the cases and cattle were injected with blood from this animal. Although the experimental animals developed typical BEF symptoms, no signs of emphysema could be detected by clinical and pathological examinations. The histopathological changes in the skeletal muscle and synovial membranes of the natural case resembled those of BEF described by Basson, Pienaar & Van der Westhuizen (1970). The lumina of the terminal and respiratory bronchioles in the lungs were obliterated by cellular debris and the muscular portion of some of these bronchioles was necrotic. The possible pathogenesis of pulmonary emphysema is discussed.

Ataxia and paralysis associated with bovine ephemeral fever infection.

Three adult cattle that had been ataxic for 5 to 7 months and a bull that had been paralysed for 24 days following bovine ephemeral fever infection were studied clinically and pathologically. Severe bilaterally symmetrical Wallerian degeneration was demonstrated in the spinal cords of all 4 cattle; in 3 animals an area of primary damage was present in the first cervical segment of the cord and in the other animal it was at the level of the lumbar cord. Pressure on the cord resulting from trauma was considered to be the most likely aetiology because of the similarity of the lesion to other syndromes causing pressure on the cord and the absence of the usual inflammatory changes seen with infectious agents.