HiHealth Herdcare

BVD virus interferes with reproduction, detrimentally affects the unborn calf, contributes to calf pneumonia and other diseases by reducing their ability to fight off disease, and can cause severe diarrhoea. The most important effect is on pregnant cows, which may abort the foetus, or cause calf deformities. If the cow is infected during the first third of the pregnancy, the calf may become persistently infected with the virus (a 'PI' calf). The PI calf will shed the virus throughout its life, sometimes developing a severe fatal disease called mucosal disease (but often appearing healthy).

The Effect in Your Herd

Economic losses from BVD infection are a combination of detrimental effects on reproduction and conception rates and an increase in calf disease because the virus affects the immune system making calves more vulnerable to pneumonia and other diseases. Estimated financial losses are around £45,000 for a 100 cow beef herd over ten years, and  at least twice this figure for a similar sized dairy herd. (Figures from SAC BVD reference)

The Route of Transmission

The most important route is through the respiratory secretions from PIs, so screening for these and removing them is vital. Farmers can separate cattle with 3 metre fencing to eliminate nose-to-nose contact from neighbouring farms, and/or vaccinate the herd to prevent pregnant animals from becoming infected. Bulls can shed the virus in semen for up to 10 weeks after infection, so should not be used for this time after exposure. Vaccination of breeding stock is used to prevent the production of further PIs whilst the disease is being eliminated from a herd.

Johne's disease is caused by the bacterium Mycobacterium avium subspecies paratuberculosis. Infection is targeted to the intestine wall, causing damage which results in a slow wasting disease characterised by loss of condition, scouring and death (or culling). Young animals are most susceptible to infection, but the disease has a long incubation period and is not usually noticed until the animals pass 18 months of age.

The Effect in Your Herd

In infected herds a high rate of wastage and increased culling rates are often seen in cattle between 2-4 years of age. Average annual losses are estimated at £2,600 in a 100 cow dairy herd, and £1,600 in a similar sized beef herd.  (figures from NADIS bulletin 2007)

The Route of Transmission

The bacterium is shed in large quantities in the faeces of infected animals, and the calves of affected animals are more likely to be infected. The slow development of the disease means that spread of infection occurs before an animal can be detected as positive, and makes it hard to eradicate. Vaccination may prevent some clinical disease, but does not prevent new infections in  the herd. Pasture becomes contaminated and ideally should be left for a year before cattle are allowed to graze.

IBR virus causes a severe respiratory disease, which may progress to a fatal pneumonia. Once an animal has been infected, it remains a carrier for life, with periods of stress (such as movement, starting a bull in work or bringing in for the winter) triggering shedding of virus. Several different strains exist which also cause reduced fertility/abortions, a drop in milk yield and inflammation of the vulva/prepuce.

The Effect in Your Herd

Your herd may experience reproductive problems such as failure to conceive and abortions, as well as severe pneumonia outbreaks amongst calves. In addition many European countries are IBR free, and animals exported to the EU will generally have to come from Accredited-free herds.

The Route of Transmission

The virus is spread by respiratory tract and eye secretions, and also by semen. Separate cattle with 3 metre fencing to eliminate nose-to-nose contact from neighbouring farms or between separately managed groups. Infected bulls can shed the virus in semen. Vaccination can be an option; as a marker vaccine has been developed which is distinguishable from wild IBR infection.

Neosporosis is a disease caused by the protozoa Neospora Caninum.  Abortion is the most common clinical sign of the disease however, occasionally, it can cause neurological disease in calves. Cattle are the intermediate host with dogs and foxes being the definitive hosts and therefore important in the biosecurity implications.

The Effect in Your Herd

Neospora is the most frequently diagnosed cause of abortion in cattle in the UK. This has high economic impact with loss of the calf, less milk produced and higher reproductive costs.

The Route of Infection

Neospora is transmitted in 2 ways

1. 'Vertical Infection' (endogenous transmission) - this is a direct transfer of infection from dam to calf across the placenta and is the most common form of transmission.

2. 'Horizontal Infection' (exogenous infection) - the cow ingests oocysts from pasture or feed contaminated with dog/fox faeces.

Biosecurity Specifically Targeted to Neospora

Dogs should not have access to carcases or afterbirth which should be removed as soon as possible, this helps prevent dogs becoming infected. Dogs should not have access to pasture for grazing and forage nor have access to areas of feed storage. Feed needs to be stored in vermin proof containers.

Leptospirosis is caused by infection by two bacteria called Leptospira interrogans serovar hardjo, and Leptospira borgpetersenii serovar hardjo. These cause abortion, stillborn or very weak calves, poor fertility, and fever and milk drop. Leptospirosis can also affect humans, occasionally causing fatal meningitis.

The Effect in Your Herd

Your herd may experience reproductive problems such as failure to conceive and abortions, and calves born to infected animals are often sickly and weak.

The Route of Transmission

The bacteria are present in the reproductive tract and kidneys, and are shed in the urine of infected animals, in the semen and can pass into unborn calves. The organisms often pass into streams and other water sources in contaminated pasture; therefore piped water is safest for health scheme cattle. Vaccination may prevent some clinical disease, but does not prevent infection of the herd.