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Newsletter 7, April 2018 – Infections and factors that may lead to resorption and failure to conceive

Dear dog breeding enthusiasts

More information about breeding matters can be obtained from our new look website and my book “Breeding is a bitch”. For further details go to http://www.rantendal.co.za.

Semen can now be frozen on demand at our premises with as little as 1 weeks’ notice. Contact Gigi at reports@rantendal.co.za to make a booking. 

We perform preliminary screening for HD and ED in dogs from 6 months of age and official certification from 12 or 18 months depending on breed. These evaluations can be performed whilst you wait for approximately 15 minutes per dog.

Infections and factors that may lead to resorption and failure to conceive

There are a number of factors that may lead to failure to conceive, resorption, small litters, abortion and poor puppy survival. Canine herpes virus can affect results on all mentioned levels and is dealt with below separately.

Obesity in bitches may lead to decreased ovulation, decreased fertility, increased incidence of silent heat, prolonged inter-oestrous intervals, smaller litter sizes, increased risk of false pregnancy increased chance of dystocia (difficulty in labour and thus increase in stillbirth rates) and increased incidence of caesarean sections. Therefore, breeders should keep breeding bitches trim at the time of conception. Restriction of calories is the way to success. Dieting should commence way before the bitch is bound to come into heat as stringent diet during heat may compromise fertility as well. This means the bitch should be in a lean condition at the time of expected heat and during her heat and pregnancy should be fed the same as always. Only in the last trimester of pregnancy will the calorie requirement increase somewhat and significantly increase during lactation following delivery of the litter.

Kennel cough may be more deleterious than just an annoying cough in a large breeding colony. This is because the viral and bacterial load may be overwhelming and result in not only upper but also lower respiratory disease. Severe kennel cough outbreaks have two more deleterious effects on the breeding colony. Firstly, bitches becoming infected whilst artificial insemination or natural mating is taking place may indeed not conceive or resorb and puppies born in the midst of the outbreak develop severe pneumonia at ages as young as 2-3 weeks and may die. Brachycephalic (short faced) breed’s puppies are at particular risk for mortality. We strongly recommend that when bitches are presented for artificial insemination to our hospital that they have ideally already been vaccinated for kennel cough including the Bordetella vaccine. Please note that Bordetella is not included in the annual 5 or 6 in 1 vaccination and is an additional vaccine. If that was not done it is advised that it is done at first presentation for insemination or breeding.

Tick control is of utmost importance in breeding bitches. This is because bitches suffering from biliary are likely either not conceive or abort when contracting biliary. Bitches in advanced pregnancy are also more likely to die from biliary or require more intensive and costly treatment. In breeds where caesarean section is likely, it may even be required to perform an evacuation of the uterus (remove dead puppies) from an already compromised bitch increasing again cost and likelihood of death.

Herpes virus infection in breeding colonies is complex and comprehensively dealt with below. In summary it is a condition that is preventable by effective vaccination. The first vaccine should be administered around the time of heat and the second as soon as it is confirmed that she is pregnant. Herpes vaccination should be repeated at each heat even is she was vaccinated at her prior heat. In my opinion it does not make sense to go about all the expenses of stud fees or purchasing frozen semen and not vaccinating against something that is preventable.

Canine Herpes Virus

Canine herpes virus is found throughout the world in domestic and wild dogs. It is very common in dog breeding colonies and infection rates of 30 – 100 % of dog populations and breeding colonies have been reported. It is speculated that the true infection rates in most countries is higher than generally reported. Despite this, its presence may not be that evident to the breeder because the reproductive effects may go either unseen or be subtle. In kennels that do not breed actively, the virus may have little significance. Most owners of infected breeding colonies do not know it. This is because the virus seldom causes symptoms in the adult dogs. In some cases of susceptible adult dogs or dogs stressed in densely populated kennels and other stressful environments, the virus may cause a mild eye infection and respiratory infection in adult dogs. In rare cases the stud and bitch may have small ulcers on the genitals.  For the most part, only the foetuses in the pregnant bitch and puppies four weeks or below will suffer ill effect from herpes virus. Direct contact with fluids containing virus is usually required to transmit herpes virus but aerosol transmission is also possible. Indirect transmission is unlikely because the herpes virus does not survive long in the environment. The most likely source of infection of the new born is by oronasal (mouth and nose) contact with secretions of the dam, infected litter mates or other dogs in a kennel. The fate of the dog following exposure to herpes virus depends on circumstance.

Fate of foetuses from bitches exposed whilst pregnant (prenatal exposure)

A bitch and her offspring may either be susceptible or non-susceptible to herpes virus depending on her immune status. Bitches vaccinated against herpes virus or bitches still harbouring natural immunity from previous herpes virus exposures or recrudescence are non-susceptible and their foetuses will be safe.  Bitches without antibodies at the time of pregnancy that get exposed to virus may resorb if the infection occurs during the first 28 days of pregnancy. If the bitch resorbs all its foetuses, the breeder will not know it and possibly think that the bitch did not conceive. If only part of the litter was resorbed the breeder will then only see smaller litter sizes in this bitch. If infection occurs somewhat later in pregnancy, the bitch may either, abort, have still born pups or have weak and underweight pups that die soon after birth. Not all the pups infected in utero need necessarily be weak or die. Herpes virus may single out individuals. Because younger bitches are less likely to have been exposed they are more likely to suffer from reproductive problems following herpes exposure. Bitches having suffered from reproductive failure (fertility problems) associated with herpes virus are less likely to have future problems but this is not excluded.

Fate of pups exposed from birth to 4 weeks (Post natal exposure)

Pups born that did not receive colostral immunity from their dams are very likely to fall ill. These pups may be become infected as they pass through the birth canal or shortly thereafter from infected oral and nasal secretions of the dam or any other dog in the kennel that is shedding virus by direct oronasal contact with fluids or from mother to pup as an aerosol (droplet infection). Delivery by caesarean section cannot guarantee herpes free puppies but may minimise the risk. These pups would require hand rearing, colostral intake by tube and total isolation of all other dogs. Therefore this way of trying to prevent herpes is not always practical or successful. The incubation period is about 6 - 10 days. Therefore, pups infected at birth or very soon thereafter will show illness within the first 7 – 21 days. Litters in which the onset of symptoms is 7-14 days have a very high mortality rate approaching 100 % whilst litters between 14 – 21 days may have a somewhat lower mortality rate. In the former group the deadly systemic form of the disease is more likely, whereas in the latter group, the likelihood of the respiratory form is greater. The first clinical signs normally seen in the puppies is inability to nurse followed by continuous crying. Their abdomens may appear bloated, are painful to touch and have dark blue discolouration. These symptoms may persist for 1-3 days after which the pups normally die. Treatment is usually ineffective. Tube feeding, raising the environmental temperature, antiviral therapy and immune serums are all advised but normally do not work. Pups that survive may suffer from nervous symptoms or myocarditis and succumb to that later. Preventative treatment of in-contact litter mates not yet affected, may help. Besides immune-incompetence, inability to thermoregulate and inability to mount a fever response explains the young pup’s high susceptibility to herpes virus as opposed to older pups. As with any cause of reproductive failure and puppy losses, breeders should have this investigated by their veterinarian in attempts to accurately diagnose a cause.

 Fate of dogs older than 4 weeks

Puppies older than 4 weeks of age and any other age thereafter will not have any symptoms from the herpes virus following exposure or only mild respiratory symptoms. They will develop immunity by producing antibodies against the virus in the blood. This immunity may last for several months only.   A unique feature of herpes virus infection in dogs is that despite the dog developing antibodies in the blood, the virus does not totally disappear from the dog’s body, but rather goes into “hiding” in the ganglia of the nerves and remains dormant. Until proven otherwise, it should be assumed that, once the dog is infected, most will remain latently affected for life and will be asymptomatic. These latent carriers may falsely test negative against herpes antibody tests. The latent virus may be “awakened” (recrudescence) in the dog’s system by numerous stressors after which they show episodes of virus shedding for up to a week at a time in genital or nasal secretions. These stressors may be transport, illness, hierarchical disputes, new introductions or translocation. This intermittent virus shedding may occur at unpredictable intervals over months or even years. Such intermittent shedding assures the survival of herpes virus in the dog population and in breeding kennels.  Usually after such shedding, the dog seroconverts (develops more antibodies again) which will make it immune for some months and enable it to transfer immunity in colostrum for 2-3 months.   

Control of canine herpes virus

Testing at the time of breeding in attempts to eliminate risk of herpes virus exposure is useless. This is because most dogs are likely to be positive in any case, and negative tests mean nothing because the test does not reveal latent virus in carriers. Vaccination is the only effective control available to breeders. An effective vaccine is available in many countries. Because the immunity induced by the vaccine only lasts 2-3 months following vaccination, it should be administered to the dams whilst in heat and again when the bitch is confirmed pregnant but not later than 10 days prior to the expected whelping date. The vaccine has been shown to significantly improve litter size weaning rates, increase puppy birth weights and reduce early puppy death. At her next pregnancy irrespective of interval, revaccination is required. Vaccination of the stud serves no purpose.

There may be value in collecting colostrum from vaccinated bitches and freezing it in a colostrum bank. This colostrum will then contain antibodies against herpes virus and could be administered to new born puppies from bitches that have puppies at risk because they were not vaccinated. This may help reduce losses in case of an outbreak.

Practical significance of herpes virus to breeders

Venereal transmission is possible but is speculated to be very rare. It may be assumed that the stud plays no bigger a role in transmission of the virus than does any other individual in an infected colony. Canine herpes virus in dog breeding colonies is so common that breeders should assume that their kennels’ are infected unless proven otherwise. Breeders who show regularly, have large numbers of actively breeding bitches, groom, run boarding kennels and train dogs on the same premises that they breed are more likely to suffer from herpes related fertility problems because of higher exposure rates and more stressful environment. Introduction of herpes virus into a dog colony that is naïve (has never been exposed before) may lead to serious outbreaks of canine herpes virus associated fertility problems if this introduction occurs during at a time that many bitches are about to be bred or already pregnant.

There is no reason why the breeder should not breed a bitch that produced a litter of puppies that had herpes. Once exposed to herpes virus her chances to suffer from fertility problems are less at subsequent breedings. Reproductive problems associated with herpes virus in infected kennels may sometimes come and go mysteriously with intervals of several years. This phenomenon can be explained by immunity that has built up in the dog colony and bitches that were pregnant at any time were neither infected or susceptible. Some breeders may erroneously think that they are free from herpes virus reproductive problems because they may have become accustomed to low fertility. These breeders only become aware of the problem once they note improvement following the use of the vaccine.

Absence of evidence of reproductive problems is not proof of absence of herpes virus infection in that kennel. Given this background, the breeder may now ask what is the relevance of all this to them as breeders and under what circumstances should they vaccinate against herpes virus.  The breeder should consider the following risk benefit assessment. Breeders that appear to be plagued by reproductive problems such as bitches that fail to conceive, appear to resorb, abort, have weak and underweight puppies or suffer from neonatal deaths should have this problem investigated. If either herpes is confirmed or no obvious cause of the reproductive problems can be found, the index of suspicion is high enough to warrant vaccination against herpes virus. Some breeders elect to vaccinate their bitches despite not having had previous problems out of fear of devastating loses. It makes sense for breeders that have already spend a large sum of money on artificial insemination or acquisition of new breeding stock at great expense, to eliminate as much risk as they can to prevent puppy losses by vaccination. Other breeders argue that they will consider control of herpes virus vaccine if they have experienced losses before they justify cost of vaccination.

In summary, eradication of canine herpes virus in kennels is not possible but minimizing the risk of losses to herpes virus is. Minimising stress, isolating pregnant bitches during peak susceptibility (3 weeks before to 3 weeks after parturition) from the general dog population and vaccinating may all aid in this.