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 Canine Herpes Virus

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VESELA
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ПисанеЗаглавие: Canine Herpes Virus   Чет 08 Дек 2011, 12:20

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Canine Herpes Virus

Herpes Virus


Herpes virus infection in the last three weeks of pregnancy or the first three weeks post-whelping is most likely to result in infection of the puppies. This happens because the mother passes on the virus to the puppies but does not give them antibodies against the disease, so they are susceptible to infection.

In most cases, a bitch who has been infected with herpes virus prior to being bred will pass on adequate antibody protection to her puppies to keep them from being infected at a time when they are likely to become severely ill or die. This includes bitches that are unlucky enough to become infected during the critical time in a prior pregnancy. Even though their first litter was infected, their subsequent ones are unlikely to be infected.

Herpes virus is very common and it would be surprising if the male had not been exposed previously, so there isn't much reason to worry about him.

Trying to shelter a bitch from herpes virus prior to breeding her is probably a mistake. It is better to allow her to be exposed to situations in which other dogs are around so that she will become infected with the herpes virus, develop antibodies and pass them on to her puppies. Once she is bred, though, it may be better to assume that she has not been exposed and to try to protect her from contact with dogs that may have herpes virus.

There is a lot of conflicting information on canine herpes virus and I don't know if I am just missing something or if a lot of poor information is out there. As far as I know, based on the books I have here, this is the situation with canine herpes virus: This virus is a common inhabitant of the upper respiratory tract of dogs, which means that many dogs should have a positive titre. If a bitch is first exposed to this virus during a pregnancy, it can affect the litter, leading to foetal death or early death of the puppies after birth. If the litter is exposed in the first few weeks of life, they may also show severe signs of illness. Once the bitch is exposed to the virus, it is very unlikely that any further litters will be affected. The virus is common enough that if the male dog is being shown or being used for breeding on a regular basis it is very likely that he will have been exposed to the virus already and that he will have a titre. If he doesn't, I suppose he could be infected by the female. The risk to the male dog seems to be pretty small, though. Based on how I understand this situation, I would think it would be a good thing if the bitch had a titre to herpes virus prior to breeding, since that would infer that she could protect the puppies from infection during the pregnancy. Since this isn't the way the situation seems to be understood by dog breeders, I have to wonder if I am missing something -- but that is how I currently interpret the situation with canine herpes virus. Your vet should have some references that discuss this virus.

Canine herpes virus (CHV-1) is a virus that has been largely forgotten for many years, due in part to the difficulty in making a definitive diagnosis.

However, it is becoming increasingly clear that the virus causes many more problems than was first thought.
Like all herpes viruses, CHV is highly infectious, and a recent study showed that more than 80% of the dogs tested had been exposed to the virus at some time in their lives. Other studies have shown infection rates of 40-100% in kennels around Europe.

In kennels not previously exposed to the virus, CHV can cause massive losses, sometimes of entire litters. Death occurs in the first few days and weeks of life, with the classic pathological changes described in Diagnosis
Once the virus becomes established in kennels, periods of high mortality are interspersed with a general fall in the average birth weight of the litter, and increased pre-weaning losses.

In kennels with long-established disease the breeder may well have become accustomed to the poor results, and the existence of a problem only becomes apparent once a vaccination programme is put in place.


Diagnosis
A number of signs may suggest that CHV is causing problems, but many of these signs are multifactoral and therefore it is important to try and make a definitive diagnosis.

CHV can be a significant cause of death in young puppies, and also smaller litter size and weight.
A number of problems have also been identified in adult dogs, such as infertility and abortion.
The unborn puppy: CHV attacks the placenta of the mother, starving the foetus of nutrients. This can lead to abortion, stillbirth or resorption of the foetus (seen by the breeder as infertility).

The newborn puppy: If the puppy is infected before birth and survives, it may be underweight at birth and have a weakened immune system, making it vulnerable to early puppyhood infections.
If the puppy is infected at or soon after birth, CHV is known to be one of the factors in “fading puppy syndrome”, in which the pup fails to suckle, cries constantly, loses weight and fades away despite intensive care, sometimes in a matter of a few hours.

Another sign is soft, yellow-green faeces, sometimes mistaken for parvovirus or coronavirus.
The abdomen is painful and there may be bleeding under the skin, or a rash on the belly.
Some puppies may show signs of brain damage, such as blindness or staggering.

The adult dog: in the dog, CHV can cause painful lesions on the genitals. In the bitch, there may not be any external signs, but the bitch seems infertile or gives birth to undersize and weak litters. Careful examination may sometimes reveal small blister-like lesions on the vaginal wall. In both males and females, CHV is also known to be one of the causes of kennel cough.


Pathology
Gross pathology consists most notably of kidney changes - multiple subcapsular haemorrhages, and mottling and discoloration of the cortical parenchyma. Spleen and liver will contain discoloured and dark red areas, with a frail parenchyma. The lungs will be oedematous and have a heterogonous appearance with both reddish and grey areas. Haemorrhagic lesions are occasionally observed in the myocardium (heart).
There is often bleeding under the skin, especially around the abdomen.


Virus isolation
CHV can be isolated from the lungs and kidneys of affected puppies, but is very labile and false negative results are common.

Blood testing
Serology is of limited value due to the high prevalence of the virus within the general population. A single negative or positive result is of little value. However, paired serum samples at 2-3 weeks interval showing a rise in antibody titre (seroconversion) will indicate active infection. The best time to take the samples (from the mother) is around the time of whelping.

PCR
PCR tests are available for identifying the virus from discharges or from affected pups. PCR will be negative when the virus is latent.


Treatment & Prevention
Treatment

There is no cure for an animal that has CHV – infection is probably lifelong and can flare up repeatedly during periods of stress. Antiviral drugs such as acyclovir have shown very limited efficacy and are expensive.
Some work has shown variable success by injecting infected puppies with the serum of immune bitches. Early intervention appears vital and will depend on the immune status of the donor.

Prevention
The disease is most clinically significant in unborn and newborn puppies. Infection takes place transplancentally, during birth and soon after birth. Therefore caesarean birth cannot guarantee freedom from infection. It can also be transmitted from mother to pup as an aerosol (droplet infection). However, good hygiene and quarantine measures between breeding units will reduce the viral burden within the environment and reduce the incidence of secondary bacterial infections.
CHV multiplies rapidly when body temperature falls below 37oC (99oF). This explains why puppies in the first three weeks of life are worst affected, as they have poor ability to regulate body temperature. The ideal body temperature of 39oC (101.5oF) can be maintained with the use of infra-red heat lamps, though it is important not to overheat the mother.
As the greatest amounts of virus are shed in the first hours post partum, colostral antibody is the most important factor in reducing disease incidence in the puppy. Even seropositive (previously exposed) bitches do not produce significant amounts of neutralising antibody, and therefore it is necessary to boost the immune system prior to whelping.
Previous exposure to CHV will not confer lasting immunity. The virus becomes latent until the circulating antibody levels fall, which can occur in as little as three months. It will then reappear during periods of stress, particularly whelping and overcrowding. High levels of maternal circulating antibody are required to provide protective levels in colostrum.
Vaccination

An inactivated vaccine is now available from veterinary surgeons in Europe (not USA), produced by Merial. The vaccine, Eurican® Herpes 205, has been shown to significantly improve weaning rates, increase puppy birth weights and reduce early puppy death.

There even appears to be a trend to larger litter sizes, indicating a protective effect on the unborn pup.
Even bitches that already have the virus can be vaccinated.

Two doses of the vaccine are given to the bitch, the first dose at or soon after mating and the second dose six to seven weeks later, i.e. mid - late pregnancy. This stimulates the bitch to produce high levels of protective antibody to CHV, which she then passes to the puppies in their first feed of colostrum.
The vaccination schedule must be repeated at each pregnancy, i.e. two injections.
The vaccine will not interfere with PCR or virus isolation tests.

Fading Puppies
BEEF (OX) LIVER REMEDY FOR FADING PUPPIES

Large piece of Beef (Ox) Liver, little bit of water, boil slowly, about 5 minutes
until the blood comes out. Squeeze the liver to get as much blood as possible . Let cool, drain the liquid and put just 4 drops (no matter the breed) into a dropper and give to puppy.

At first you give it every 1/2 hours for 2 hours, then 2 for 24 then every 4 hours for a minimum of 3 days. You can do this for however long you have to, until you feel
the puppy is thriving.

Don't use any of the liver itself, just the liquid.

Kay Cook
Exelby Labradors
Tel 01576 610546
e-mail: exelbylabradors@yahoo.co.uk
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