On farm lambing problems from our experience
(on its way soon)
Bluetongue Also known as Catarrhal fever
This
is a disease of ruminants caused by a virus called Orbivirus of which there are
24-25 different strains or serotypes. Serotypes 1,2,4,9,16 are present in
Southern Europe as far north as Italy
and Spain and serotype 8 which is responsible for the Northern European
outbreak. Interserotype effectiveness of vaccines is limited. The virus doesn't
contaminate milk or meat and isn't transmissible to humans, nor is there direct
passage between ruminants. Transmission is normally via a bite from a
blood-sucking midge, sp. Culicoides but is also possible via contaminated sperm
and at least in theory other blood-feeding insects such as ticks and keds. While
cattle are possibly the main reservoir sheep are clearly highly susceptible and
the ovine disease typically presents
as follows:-
Day 1
High temperature, up to 42oC
Day 2
Swelling and congestion around the head; nose and lower jaw in
particular.
Day
3
Mouth and tongue affected; tears, a purulent nasal discharge often
bloodstained, excessive frothy salivation,
stiffness and strained neck due to muscle damage.
Day
7
Arthritis, lameness, abortions, congestion at the level of skin leading
to eventual wool loss. Secondary pulmonary or digestive complications, coughing and/or bloody diarrhoea
Day
10-12 Deaths,
average 5-10% of the flock but 20% of the sick animals, severe loss
condition of the rest.
Day 15-
very
slow convalescence. Residual symptoms variable, following the particular flock.
Hoof lesions, laminitis and coronitis, are common. Adults and males are most
affected and infected animals can remain infection reservoirs for at least 60
days after recovery via blood, semen, ova and embryos.
PREVENTION
of spread: use of repellents and insecticides on infected animals and their
confinement to insecticide treated buildings to reduce further infection of the
local midge population. Housing is also useful since sick animals are light
sensitive. Treatment of non-infected animals reduces the number of insect bites
but does not actually protect against the disease; only one bite is in theory
enough.
THE WINTER TRUCE; at less than
10-12oC there are far less Culicoides flying and thus the spread
effectively stops. They are killed by hard frosts. Nevertheless the midges
survive in buildings and the virus seems transmissible to their larvae. This
explains the re-appearance of the disease the following year as temperatures
re-increase. The midges are easily windborne, cross-Channel for example, so
restriction of animal movement and/or insecticide pre-treatment of animals to be
moved is likely to be of only partial value.
The only effective solution is
likely to be the development of a vaccine to strain 8 in particular and this is
likely to be available in spring 2008 in the UK. Department of
Agriculture in Ireland have not yet announced their plans. Comprehensive
information is available on their website.
Scrapie
