Viral Diseases Causing Infertility

Viral diseases causing infertility in animals are bovine viral diarrhoea (BVD), IBRT, Epivag, Blue tongue, Catarrhal vaginocavitis, Parinfluenza (PI3) virus abortion, Transmissible genital fibropapillomas, etc.

Common viral diseases causing infertility in animals are:

• Bovine Viral Diarrhoea (BVD)
• Infectious Bovine Rhinotracheitis (IBRT)
• Epivag
• Blue Tongue
• Catarrhal Vaginocavitis
• Parinfluenza (PI3) Virus Abortion
• Transmissible Genital Fibropapillomas

Bovine Viral Diarrhoea (BVD)

Bovine Viral Diarrhoea (BVD) was initially recognized as a cause of diarrhoea during the 1940s.

It also causes infertility. The BVD virus is a pestivirus, which is related to the viruses of Border disease of sheep and classical swine fever.

Transmission

• Infection with the non-cytopathic strain in utero between about days 30 and 125 of gestation leads to the birth of a calf that is persistently infected with the virus.
• Persistently infected animals shed the virus throughout life.
• Persistently infected cows can transmit the disease vertically through trans placental infection to their calves.

Pathogenesis

• Infection of cows at other stages of pregnancy causes early embryonic death and abortion, with aborted fetuses exhibiting abnormalities of the central nervous and ocular systems.
• Bulls have been shown to excrete the virus in their semen following spontaneous, persistent and chronic infection and also following experimental infection.
• Mucosal disease is usually seen in younger animals. The disease is characterized by pyrexia, anorexia, watery diarrhoea, nasal discharge, buccal ulceration and lameness. The morbidity rate is generally low, but, amongst affected animals, the mortality rate is high.

Clinical Signs

• Acute infection, with either biotype, can severely affect the embryo or fetus.
• During the first month of gestation, infection results in the death and resorption of a high proportion of embryos.
• The only signs of reproductive disease that such affected cows or heifers exhibit is returning to estrus at normal or extended intervals.
• Pregnancy rates are therefore reduced in affected animals.
• From the second to the fourth month of gestation, infection may be followed by abortion, death with mummification, growth retardation, developmental abnormalities of the central nervous system and alopecia; some infected cows or heifers will carry calves to term,
• From the fifth and sixth months of gestation, there can be abortion or the birth of calves with congenital abnormalities of the central nervous system and eyes.

Diagnosis

• history of the overt disease.
• pyrexia, inappetance and respiratory distress.
• abortions and birth of congenitally deformed calves. The fetuses may be fresh, autolysed or mummified.
• The virus can be isolated from the fetus, particularly lymphoid tissue such as the spleen. Immuno cytochemical identification of kidney, lung or lymphoid tissue, can sometimes be detected.

Treatment and Control

• The absence of antibody titres is generally assumed to indicate the absence of infection. With BVD this is not the case; a seropositive animal would be a safe purchase but a seronegative one requires to be free of virus to assure freedom from risk.
• Killed-virus vaccines can be used in pregnant cows.

Infectious Bovine Rhinotracheitis (IBRT)

• Infectious bovine rhinotracheitis virus causes an acute respiratory disease of cattle with conjunctivitis.It also causes a disease of the genital organs of the bull and cow.
• the disease of the genital system has been variously called infectious pustular vulvovaginitis, vesicular venereal disease and coital vesicular exanthema. BHV-1 causes both the respiratory and genital forms of the disease.
• BHV-1 also causes abortion, more commonly after the respiratory, rather than the genital, form of the disease. BHV-1 infection is also associated with infertility in cows and heifers.

Transmission

• The genital form of the disease is readily transmitted venerally, but this is not the only route, since it can occur via contaminated bedding and the mutual licking and sniffing of the vulva and perineum of infected and non-infected animals.
• Also, it can be transmitted by virus contaminated semen. Once it has gained entry, it is transported haematogenously in leucocytes.

Pathogenesis

• Some animals can become lifelong latent carriers of the virus, despite the formation of specific antibodies. The infection enters a latent phase in the ganglion cells of the nervous system.
• Under certain circumstances, such as stress, calving, transportation, vaccination or corticosteroid therapy, the latent infection can be reactivated so that the virus migrates along nerves to the periphery, where it multiplies and is excreted. These animals represent a reservoir of the virus.

Clinical Signs

• The onset of vulvovaginitis is sudden and acute. Signs appear 24-48 hour after veneral transmission.
• The vulval labia become swollen and tender and, in light-skinned animals, deeply congested.
• The quantity of vulval discharge is variable, ranging from small quantities of exudates, which adhere to the vulval and tail hairs, to a copious mucopurulent discharge.

Infertility

• Opinions have varied over the role of BHV-1 as a cause of infertility. Artificial insemination of contaminated semen is undoubtedly associated with embryonic death.
• It can cause a bilateral necrotizing oophoritis, to which the corpus luteum appears particularly susceptible, especially during the first few days after ovulation. This damage to the developing corpus luteum may directly affect its function, perhaps resulting in lower than normal progesterone production.

Abortion

• Abortion is a common sequel to infection.
• In beef herds, abortion ‘storms‘ occur, with between 5 and 60% of cow aborting.
• Abortions occur from 4 months of gestation to term. Some calves are stillborn, and a few may be born alive, but succumb subsequently.

Epivag

• ‘Epivag‘ is a specific bovine venereal disease causing epididymitis and vaginitis in cattle.
• It causes diffuse infection of the vagina, but not the presence of distinct lesion as occur with IPV.
• A severe mucopurulent vaginal discharge may be present during the earlier stages of the disease.
• Most infected cows fail to conceive to service, and subsequently develop adhesions, hydrosalpinx and ovarian and bursal adhesions.
• Most bulls have a mild balanoposthitis after infection, although, since this is far less severe than IPV infection, it may not be observed.
• Subsequently, most bulls develop an induration of the epididymis, particularly of its tail. Orchitis may occasionally occur.

Diagnosis

• The genital tract lesions of IPV are fairly characteristic of the disease, but must be differentiated from granular vulvovaginitis due to Ureaplasma sp and catarrhal vaginocervicitis.
• Histologically, there is always focal necrosis of the liver and in many cases there are necrotic lesions in the brain, lungs, spleen, adrenal cortex and lymph nodes.
• There are characteristic virus inclusion bodies at the periphery of these necrotic lesions in fresh experimental cases but, because of autolysis, they are not always demonstrable in field cases of abortion.
• The virus has been found in all fetal tissue and is concentrated in the cotyledons.
• Serological examination of paired serum samples from at least 10 cows in the herd should reveal sero conversion or a four-fold increase in titres if IBR infection is active in the herd.
• For subsequent fluorescent antibody tests, pieces of fetal tissue, particularly kidney and adrenal gland, should be taken together with a piece of placenta.

Treatment

Spontaneous recovery of the genital lesions will occur and therefore treatment is not really necessary; however, the administration of emollient creams to the vulva, vagina and penis may be useful.

Control

Infected animals should be isolated.

Vaccination is the most effective way of controlling the disease; a number of live, attenuated vaccines are available, often combined with a bovine para influenza virus vaccine. Heifers should be vaccinated after 6 months of age and before their first service.

Blue Tongue

• Blue tongue is mainly a disease of sheep and deer, but cattle and wild ruminants are important reservoir hosts for the virus.
• The virus is primarily transmitted by insect bites. Culicoides species are the main vectors and there may be some transmission by ticks, keds and mosquitoes.
• Bulls that are infected by blue tongue virus can transmit the virus in their semen.
• Infection of susceptible cattle causes a viraemia, during which the virus can cross the placenta.
• Infection of the post-hatching embryo can result in its death and seasonal infertility can result.
• Infection later in pregnancy can lead to abortion or mummification of the fetus.
• The neruropathogenicity of the virus produces hydroencephaly an abnormal contractures of extremities.
• Calves may be born alive, which are weak and ataxic or which are persistent carriers of the infection.
• In the aborted fetus, diagnosis of blue tongue can be made by demonstration of central nervous lesions or by virus isolation from fetal blood, spleen, lung or brain.
• Serology can be used to diagnose maternal infection, although the presence of antibody-negative,
• viraemic animals during an epizootic outbreak can confuse diagnosis.

Catarrhal Vaginocavitis

Catarrhal Vaginocavitis is caused by an enterovirus from the enteric cytopathic bovine orphan (ECBO) group.

Transmission and Pathogenesis

Although the disease is transmitted venereally, it can also be spread by faecal contamination of the vulva, or by animals licking the perineum of infected and non infected individuals; hence the disease can occur in virgin heifers.

Clinical Signs

• Affected animals have a profuse, postcoital non-odorous, yellow, mucoid vulval discharge. The cervix and vagina are inflamed but there are no pustules,
• no fever. The typical yellow gelatinous exudate frequently accumulates in the vagina, varying in quantity from a few to several hundred milliliters.
• pregnancy rates are reduced and there are prolonged, irregular returns to estrus and late embryonic death.
• In some herds, fetal mummification, abortion and stillbirth have been reported as being a problem.
• Bulls may or may not become clinically infected. The penis and prepuce do not show the lesions that occur following BHV-1 infection.

Diagnosis

• The most reliable method of diagnosis is serological examination of paired blood samples, collected at least 15 days apart, for evidence of rising antibody titres; the first sample should be collected as soon as possible after the disease is suspected.
• The virus can be isolated from vaginal mucus, but the recovery rate is frequently low.

Treatment and Control

• There is no specific treatment or vaccine.
• Infected bulls should not be used for service for several months, even after clinical signs of disease have disappeared.
• Potentially infected animals should be isolated after purchase and, in closed herds; serological examination of potential additions to the herd might be contemplated.

Parinfluenza (PI3) Virus Abortion

This widely distributed virus has been recovered from aborted fetuses in which it caused a septicaemic disease. Experimentally, it can cause fetal death and abortion after interafetal inoculation, but after introduction into the maternal respiratory system.

Vaccines to PI 3 virus are available commercially, often combined with IBR vaccines. Vaccination can be done during calf hood or in adult cattle to give lifelong protection.

Transmissible Genital Fibropapillomas

Wart-like tumours commonly occur on the penis of young bull and occasionally similar growths occur on the vulva, perineum and vestibulovaginal epithelium of heifers. They are caused by a virus of the papovavirus group and are transmitted by contact with infected animals.

These fibropapillomata regress spontaneously in 2-6 months; the speed of regression may be expedited by the use of a wart vaccine Except in so far as the larger tumours might interfere mechanically with coitus, they do not cause infertility in female animals.