We are most grateful for the translations sent to us of Mariska Vermaas' article in the Agarische Dagblad in today's (17th May 2008) Agarisch Dagblad (in Dutch) Link sent by Ruud Peys.
Unborn calves can be infected with BT via the mother
The article states that a cow can pass on the virus to her unborn calf. This comes as a result of research by CVI and GD.
The reason for this research was the export of in-calf cows to NI where calves have been born carrying BT virus. " So far infection of the unborn calf has only occured after vaccination with a life virus vaccine. The BTV8 serotype seems to be somewhat extraordinary" says CVI virologist Piet van Rijn.
The research was carried out on calves from 400 cows born after January, 1st, in the vector free period. 221 cows were antibody positive for BTV8. " In 34 calves, about 15%, born to seropositive dams the virus was detected. The calves were infected in the womb from their dams."
" Maybe during the first time of their lives these calves don't pose a risk transmitting the disease because of antibodies catching the virus. But we don't know what happens once maternal immunity ceases. Maybe these calves constitute a source of the virus for the midges and thus a danger for other animals" says van Rijn.
The whole discussion about overwintering of the virus gets a new dimension
"Vaccination of animals prior to service will minimize the risk of calves born carrying the virus for the following year".
Unborn calves can become infected with Bluetongue via the dam
This new finding is the result of an investigtion by the CVI (Central Veterinary Institute) and GD (Animal Health)
The study was a consequence of the export of in-calf cows to Northern Ireland which gave birth to calves infected with the bluetongue virus. The cows were – according to tests – free of the virus. Until now the transmission (of the virus) to unborn embryos has only been observed after vaccination with the attenuated Bluetongue virus. This variant of the Bluetongue serotype 8 seems to be an exception", says CVI virologist Piet van Rijn. (this doesn't make sense, but is literally translated)
During the investigation the calves of 400 cows were tested all born after 1 January, the vector free period. 221 cows had antibodies to Bluetongue. "In 34 claves, approximately 15%, of those cows (with antibodies) we found the presence of the virus. They got this from their dams during the pregnancy."
"It is unlikely that the calves will pose a threat in the spread of the disease during the early part of their lives as the virus will be caught by the antibodies (this is not well expressed in Dutch but it is clear that what is meant is that the suckling calf receives the mother's antibodies) We do not know yet what happens when the maternal protection ends. It is possible that the calves will form a source of the virus for the midge and therefore a risk for the rest of the ruminant population", says Piet van Rijn.
This means that the whole discussion about the over-wintering ability of the virus takes a new turn. Piet van Rijn: "Vaccination of animals kept for breeding will reduce the chance of infected calves during the following season".
Another alternative translation of Mariska Vermaas' articleUnborn calves can be infected with BT via the motherresearch from the central veterinary institute (CVI) and the health service for animals (GD) show, reports cattle- and bluetongue - reporter Mariska Vermaas in Agrarisch Dagblad.The research was carried out after calves with the BT-virus were born to pregnant cows exported to Northern Ireland. The cows themselves had tested virus-free. ''Up until than, this transfer to the unborn animal had only been found after vaccination with weakened BT-virusses. The serotype variant of the BT virus appears to be an exception,'' says viroloog Piet van Rijn from the CVI.
In the course of the research, calves born to 400 cows after 1 January in the midge-free periods were examined. 221 of the cows had antibodies against bluetongue. 34 calves were found to have the virus. ''They have got that during the pregnancy from their mothers,'' Van Rijn says. ''At first, these calves are probably no danger for the spread of the virus because the virus will be neutralised by the antibodies. We do not know yet what happens after this maternal protection stops. It is possible that calves are a source of virusses for the midges and therefore are a danger for the rest of the cattle.'' Van Rijn stresses that this gives the whole discussion for overwintering of the virus a new dimension. ''Vaccinating animals which well be inseminated reduces the risk of infected calves in the next season.''
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