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Infectious disease and fertility - Coggle Diagram
Infectious disease and fertility
Bovine Viral Diarrhoea (BVD)
elimination of infection from the herd is optimal, but vaccination is highly effective and produces a substantial cost benefits.
transmission
contracted from contact with infected cattle
sexually transmitted
transmitted across the placenta from dam to calf
if infected in-utero they are persistently infected with the virus
These animals excrete large volumes of virus all of their lives and are the main route of infections in other animals. Identifying and removing these animals is the mainstay of eradication schemes for the BVDV.
clinical signs
may not be any signs as protective antibodies produced 3-4 weeks
may lower immunity to other infectious diseases
salmonella
respiratory infections
coccidiosis
diarrhoea not often seen
infection early pregnancy causes embryonic death and return to oestrus
foetal death/abortion
mummification of foetus
birth defects of nervous system and eyes
low head carriage and wide stance
weak, premature calves and live persistently-infected calves
infection of foetus before 110/120 days of pregnancy results in birth of live PI calf, due to failure of developing immune system of the foetus to function properly before 110 days
PI typically fail to thrive and lead to smaller/less healthy calves v their same age cohort
may be blind or lack coordination
cull for welfare reasons and source of infection
Bulls are vigorously tested for BVD before entering AI studs. Testing for BVDV is essential for all purchased bulls prior to their use on farm.
If super infected with cytopathic BVDV -->
Mucosal disease
arises from changes in the BVD virus within the PI animal
6-12m old calves
clinical signs
sudden onset depression
fever
anorexia
excess salivation
ulcers on mouth and muzzle
purulent discharge from eyes and nostrils
profuse diarrhoea with threads of gut mucosa/blood present during terminal stages
rapid weight loss followed by death within 5-10d
Diagnosis
serology
exposure to virus
active infection (acute or PI) --> PCR
samples: blood/hair plucks/skin biopsies
current eradication schemes use skin plugs created from ear tags to identify PI animals
Treatment
treat any concurrent infections if present
e.g. chronic pneumonia 2ry to persistent BVDV infection
always cull PI animals
vaccination and biosecurity
IBR
LEPTOSPIROSIS
SALMONELLA
NEOSPORA CANINUM (NEOSPOROSIS)
causes approx 10% of abortions in UK cattle
Clinical signs
abortion (3-9m of pregnancy)
still birth/premature calf
calf may have brain disease at birth
no other signs seen in dam
repeat abortions possible in same cow
Diagnosis
identification of parasite in calf tissue
a large number of healthy calves can be infected with Neospora it is important to eliminate other causes of abortion, particularly BVD or leptospirosis before a diagnosis of neosporosis is made.
antibodies in mother's blood
no treatment of proven benefit
prevention
keep cattle food + water away from dogs and foxes
high hygiene standards at calving
dispose of placental membranes and aborted or dead calves before dogs can get them
vertical transmission (dam --> calf)
90% of calves born to dams with Abs will have been infected in utero, this will maintain infection in herd
identify infected cattle
cattle with antibodies are 20 times more likely to abort between 90 and 270 days of pregnancy than cattle without antibodies. Finally, on average, several studies have suggested that infected cows produce less milk than antibody negative cows.
select only seronegative cattle for breeding
if do not cull seropositive, only breed to beef
SCHMALLENBURG
diseases which have 2ry/indirect affects on fertility
johnes
fluke
BRUCELLOSIS
CAMPYLOBACTER
Fundamentals for control (regardless of disease)
1) Initial surveillance (assessment)
2) eradication of the disease (where possible)
3) biosecurity to prevent reintroduction or reduce prevalence
4) Vaccination (if available) is a key component to effective biosecurity but is not always the most
effective barrier
5) Further monitoring and surveillance
Abortion
Definition
production of 1+ calves between 50 and 270 days of gestation with calves being born dead or surviving less than 24h
An annual abortion rate of > 5% is considered to be the point at which intervention should take place.
foetal membranes hanging from the vulva are often the first sign of abortion
differentiate infectious and non infectious
non-infectious
genetic defects
environment e.g. high temperatures
nutrition e.g. mycotoxins
mouldy silage
other e.g. treatment with abortifacient drugs such as prostaglandin
