BVD Virus –

A Newly Recognized Serious Health Problem for Alpacas

By: Nancy Carr MD and Susy Carman DVM PhD.

Bovine viral diarrhea virus (BVD virus or BVDV), a serious problem in cattle, has now been proven to also cause illness, abortions, and most important of all, the persistently infected (PI) state in alpacas. The virus’s ability to produce persistently infected cria, the

main way this disease would be spread, and its ability to cause abortions are extremely

important for the alpaca industry.

At this point, the vast majority of knowledge about BVDV and the disease that it

causes, bovine viral diarrhea (BVD), is about its effects in cattle, where it is considered

one of the most significant viral infections, causing major economic losses. The

information presented next is therefore what is known about BVDV in cattle; it is likely

that most of this applies to alpacas. Following this is the information about BVDV and

alpacas. Despite the name, many animals with BVD do not have diarrhea. Other

manifestations of the virus include subclinical infections, immunosupression, abortions,

congenital defects, persistent infection, and mucosal disease. The majority of cows

infected are either subclinically ill (do not appear unwell) or only mildly unwell with low

fever and diarrhea. Because BVDV depresses the immune system, some animals will

become ill with other infections, usually pneumonia; others will have a classic case of

BVD with fever, discharge from the nose and eyes, erosions of the muzzle and in the

mouth, and severe diarrhea; others may have severe hemorrhagic (bloody) diarrhea and

die. Severity of illness is influenced by the age of the animal and its immunological and

physiological status, and the particular strain of the virus involved.

The most important aspect of BVDV is its effect on the developing fetus. BVDV can

cause abortions at any stage of gestation – from early embryo loss up to stillbirths at

term. Even a subclinically infected cow can abort, and abortions may occur up to several

months after exposure to the virus. A unique feature is that if the cow is exposed to the

virus at a critical phase of her gestation (approximately 40 - 120 days) and does not abort,

she will produce a persistently infected (PI) calf. Because the developing fetus is not

immune competent at that stage of development it becomes immunotolerant to the virus

(does not recognize the virus as foreign); it is unable to make an immune response to rid

itself of the virus, and once born, is a permanent carrier and sheds huge concentrations of

the virus in every secretion – tears, nasal discharge, saliva, urine, and feces. PI calves

are the major source of the spread of BVD – they shed several billion viral particles a day

– about a thousand times more than what is shed by an acutely infected non-PI animal.

The only way to be PI is to be born PI. Some PI calves appear completely normal, but

most are poor-doers – poor weight gain, weak, and susceptible to other diseases such as

pneumonia; many PI calves die before they are a year old. Infection of the pregnant cow

with BVD later in pregnancy can result in calves that are not PI but that have congenital

defects such as cerebellar hypoplasia (underdevelopment of the part of the brain that

controls balance and co-ordination), cataracts, blindness, hypotrichosis (sparse hair

growth) or general growth retardation.

Acute infection with BVDV occurs through the nose or mouth by contact with

secretions from an infected animal (usually a PI animal) – saliva, nasal discharge, tears,

urine or feces – either directly from the infected animal itself or from items that have

been contaminated with those secretions, such as water troughs. An acutely infected but

non-PI animal sheds virus for a relatively short length of time (4 – 10 days, possibly up to

2 weeks) in comparison with a PI animal which sheds virus for its entire life. Incubation

period is 5 to 7 days. The virus cannot survive long in the environment – a maximum of

2 weeks. Because it is a virus, antibiotics are of no use in treating it.

There are hundreds of different strains of the virus, which can also be categorized under

type 1 (BVDV1) or type 2 (BVDV2) and by the terms cytopathic or non-cytopathic.

BVDV2 tends to produce a more severe clinical illness than BVDV1. PI animals always

have a non-cytopathic strain of BVDV. An entity called mucosal disease occurs only in

PI animals – they become superinfected with an antigenically similar cytopathic strain of

the virus (usually from a mutation in their own non-cytopathic strain, or from a modified

live vaccine); this leads to severe diarrhea and inevitably death. Vaccines for cattle are

available for BVD; however they do not confer 100% immunity.

Articles published to date on BVD and camelids have generally concluded that BVD

is not much of a concern. In an article titled ‘A Medical Marvel’ in the winter 1999

edition of Alpacas Magazine Randy Larson DVM stated what was likely the commonly

held viewpoint at that time: “BVD is an example of a significant disease of cattle that

causes undetectable problems in alpacas. BVD and other common cattle viruses just do

not cause problems in alpacas.” Medicine and Surgery of South American Camelids

(page 469) makes mention of BVDV only as a cause of congenital defects and impaired

immunologic competence in calves and lambs.

In 2000, Belknap et al. from Colorado State University reported on three cases of

BVDV isolated from llamas (a stillborn fetus and two sudden deaths in adults that had

been losing condition) and concluded that BVDV should be considered as a cause of

death in young and old New World camelids. The Complete Alpaca Book makes mention

of that statement (page 451) and also that it may be one of the causes of diarrhea in cria

(page 400).

In 2002, Goyal et al. in Minnesota reported on what appeared to be the first case of

BVDV isolated from a stillborn alpaca; there were no gross or histopathologic changes of

any significance seen, but BVDV was detected by reverse transcriptase polymerase chain

reaction (rt-PCR) from a pool of tissues, and BVDV was isolated from cell cultures.

Immunohistochemistry, a test commonly used to detect BVDV in tissues taken at the

time of autopsies, was negative.

In 2003 Wentz et al. reported on the effects of experimental infection with BVD on

llamas and their fetuses, and on the seroprevalence of BVDV [detection of antibodies that

would signify the animal had been exposed to BVDV at some time in the past] in llamas

and alpacas. They concluded that llamas may be infected with BVDV but have few or no

clinical signs, and that inoculation of llamas with BVDV during gestation did not result

in fetal infection or PI crias. Seroprevalence in a sample of 223 llamas and alpacas was

0.9%. They also concluded that the most likely source of BVD infection in camelids may

be cattle.

Dr. Donald Mattson from Oregon State University (OSU) stated in June 2004 (personal

correspondence) that in their llama herd at OSU there had been one sick llama with BVD

(it had diarrhea) but that its two herdmates did not become sick. He also knew of a case

in southern Oregon with a herd of 20 llamas where only one showed signs of illness. He

stated that they had only seen BVDV infected camelids when they had been in contact

with cattle that are shedding the virus, and that he had tested hundreds of samples from

llamas and alpacas and never found a PI camelid.

However, now there is irrefutable proof that BVDV can cause illness, death, abortion

and most important of all, the PI state in alpacas. The consequences of this for the alpaca

industry may be profound.

The next article in this magazine, ‘BVD Virus and Alpacas – The Detective Story’

details how this was discovered at a farm in Ontario. There was illness, including one

death, several early pregnancy losses, and an aborted fetus that tested positive for BVDV.

One of the females who had been subclinically infected (exposure to BVDV as confirmed

by antibody testing) at 2 months gestation subsequently delivered a persistently infected

(PI) cria. This is the first recorded case of a PI alpaca, but there is overwhelming

circumstantial evidence that BVDV had been brought to the farm by another PI cria that

died without being tested. And it is highly likely that that cria’s mother’s source of her

infection with BVD during her pregnancy in Alberta (resulting in her producing that PI

cria) would have been from another PI alpaca.

The majority of alpacas infected at Farm A in Ontario were subclinically infected and it

was only apparent by antibody testing that they had been infected. (Note: having

antibodies does not mean that the animal is unwell or contagious; it shows that the animal

was exposed to the virus at some point in the past and mounted an immune response; this

could be from a subclinical infection (never appeared unwell), a clinical infection

(appeared unwell) or from immunization. For example, most of us would have

antibodies to chickenpox from having that illness as children.) The alpacas that were

unwell had symptoms that ranged from having the appearance for a few days that their

mouths were uncomfortable eating their pelletized supplement, to being off feed and

depressed, to one death from hepatic lipidosis (that condition would have resulted from

decreased feed intake). None of them had diarrhea. Many of them, even those

subclinically infected, showed stress breaks in their fleece.

The cria who was presumed in hindsight to be PI and the source of the infection (he died

without being tested) arrived at Farm A at the age of 3 months. He had been born at full

term on Farm B, also in Ontario, at a very low birth weight of 9 pounds. He had done

fairly well for the first 6 weeks of life and then developed repeated infections, mostly

pneumonia, had a frequent runny nose, and he had very poor weight gain. He died at the

age of 8 months after severe diarrhea. (This was his first episode of diarrhea since having

a bout with coccidia when he was much younger). Farm B, where he spent the first three

months of his life, had positive BVD antibody levels in alpacas that had been in contact

with him. His mother had been on Farms C and D, in Alberta, in her early pregnancy

(when she would have contracted her subclinical BVD infection resulting in her

producing this PI cria); Farm C had many abortions and Farm D had two stillbirths and a

cria that died at 36 hours of age in the same year that this female delivered her presumed

PI cria. Farms C and D have alpacas with positive BVDV antibody levels, including the

dams of the aborted fetuses, stillbirths and cria that died. Although it is possible that the

mother (who is not PI) became acutely infected at Farm D and transmitted BVD to Farm

C during the short time she would have been shedding virus, it is more likely there were

separate cases of PI animals on both those farms causing the infections. None of the

farms involved had any contact with cattle.

The proven PI cria, called Gabriel, born on Farm A (to a female who had been infected

by the above presumed PI cria) also had a very low birth weight of 12 pounds for the

farm he was born on. He had excellent weight gain to 33 pounds at the time of his

euthanization at a little over 6 weeks of age, after two sets of blood tests confirming he

was PI. (The fate of all proven PI animals is to be euthanized.) He had chronic diarrhea,

but was not unwell with it and was perky and active.

At this point it is unknown just how prevalent BVD is in alpacas. Alvarez et al.

reported in 2002 that 11.5% of alpacas in a rural community of Cusco in Peru had

antibodies to BVDV. The other reported case of BVDV in a stillborn alpaca fetus was in

Minnesota, and the llama cases were in Colorado, so this is not just a Canadian situation.

The practice of sending females with cria at side off to other farms for breeding is one of

the main ways BVD would spread – a PI cria may not show any signs of being unwell

until it is older and yet be infecting every animal it comes in contact with. Also, a

pregnant female going to a new owner may be carrying a PI fetus that, once born, will

infect all the alpacas at the new home. This case shows how BVDV traveled

approximately 3500 kilometers (over 2000 miles) from Alberta to Ontario. Some PI

cattle continue to appear healthy; it is unknown how many PI alpacas may continue to

appear normal. It is also unknown what is the exact range of gestation in alpacas that

infection of the dam will result in the birth of a PI cria. Cattle have a 9 month gestation

and it is in the period of approximately 40 –120 days of gestation that there is the high

risk of the fetus becoming PI if the mother is infected with BVD.

Alpacas have a reputation for being easy aborters, and it is not unusual to hear of poor

doing cria – it is entirely possible that many of these cases may have been due to BVDV.

Unless the virus is specifically tested for there is no way of knowing that it is present – in

both the stillborn fetus from Minnesota and the aborted fetus from Ontario there were no

pathological changes to suggest BVD – it was only by testing for the presence of the

virus itself that it was found. In the euthanized PI cria there were no pathological

changes to suggest he was PI – but virus isolation from blood and most tissues was

positive. The adult alpaca that died after what must have been an acute BVD infection

had autopsy findings of hepatic lipidosis, but it would have been BVD that caused her

appetite to decline, resulting in the hepatic lipidosis. In her case, there would not have

been virus detected as it would be too long after the initial acute infection – she would

have to have had antibody testing. It is possible that some of the unexplained cases of

hepatic lipidosis in alpaca herds have been caused by BVD. Schwantje and Stephen’s

paper on ‘Communicable Disease Risks to Wildlife from Camelids in British Columbia’

reported a positive BVDV antibody rate of 6% in a sample of 175 llamas from twelve

farms, with the rate per farm varying from 0% for many farms to a high of 22% on one

farm. This paper also reported on a survey of 90 llama and alpaca farms asking about

illness and death in the preceding year; the primary cause of death (26% of cases) was

neonatal failure to thrive or stillbirths. The report also reviewed the diagnoses of llama

and alpaca submissions to the B.C. Animal Health Centre between 1993 and 2000: 9% of

the diagnoses were idiopathic (meaning no cause found) abortion. It is quite possible

there is a connection between BVDV and some of those cases of neonatal failure to

thrive, stillbirths and abortions. Until aborted and stillborn fetuses and autopsied animals

are tested specifically for the presence of BVD virus or antibodies, depending on the

clinical situation, we will not know how prevalent this is. If it is more prevalent than has

been suspected then probably research on the use of vaccines for BVD in camelids will

be required. Only a completely closed herd (no animals coming into the herd) with good

biosecurity measures (all visitors with footwear not contaminated by manure; no fence

line contact with other livestock) can be sure to be safe from BVD.

Testing for BVDV is complicated, with different tests being used in different situations.

Having antibodies (blood test) to BVDV shows that the animal was exposed to the virus

(from a clinical or subclinical infection, or from immunization), but it is unknown how

long antibodies are detectable for after exposure. PI animals would not have antibodies

(unless they were tested as newborns soon after ingesting their mother’s antibodycontaining

colostrum). To detect the PI state the animal has to be tested for the virus

itself, and there must be two positive tests three weeks apart to prove the PI state, in case

the first positive test was an acute infection and not from being PI. Virus isolation is the

‘gold standard’ test for detecting BVDV – it can be done on blood (live animal) or tissue

(dead animal). The ELISA blood test for the virus is used to detect PI animals over the

age of 3 months (the maternal antibodies from colostrum interfere with the test before

that age, and also sometimes interfere with virus isolation.) The ELISA test on skin

biopsies or ear notches can be used to detect PI calves under the age of three months.

The PCR test (blood) is not affected by maternal antibody and is also used to detect PI

animals under the age of three months. Immunohistochemistry is used on formalin fixed

tissue from autopsies; however as noted above this test was negative in the stillborn fetus

in Minnesota despite BVDV being detected by PCR and virus isolation;

immunohistochemistry was positive in the aborted fetus in Ontario. Your veterinarian

should consult with a veterinarian virologist or with the lab that he/she uses for BVDV

diagnosis in cattle. Most labs doing BVDV testing are affiliated with universities, or are

state or provincially funded; not many private labs offer BVDV testing.

At this time, a reasonable recommendation is that all aborted or stillborn fetuses, all

unusually low birth weight and ‘poor doing’ cria and all unexplained deaths be tested for

BVD virus and/or antibodies, depending on the case. If BVDV is found then further

testing should be done to determine how the virus entered the herd - specifically is there

still a PI animal present, or has it gone back to another farm. Any cria subsequently born

to females who were pregnant when BVD was active in the herd should be tested to see if

they are PI. It is important that you bring this information to the attention of your

veterinarian as it will be at least a year before it is published in a veterinary journal. It

would also be very helpful if you or your vet notified the lab in your area where aborted

fetuses or autopsies are sent for testing about this, so that testing specifically for BVDV

will become routine in abortions, stillbirths, and unexplained deaths in alpacas.

REFERENCES:

Alvarez S., Rivera G.H., Pezo D., Garcia W. (2002). “Deteccion de anticuerpos contra

pestivirus en rumiantes de una comunidad campesina de la provincia de Canchis, Cusco.”

Rev Investig Vet Peru, 13(1), 46-51

Belknap E.B., Collins J.K., Larsen R.S., Conrad K.P. (2000). “Bovine viral diarrhea virus

in New World camelids.” J Vet Diagn Ivest, 12(6), 568-70

Fowler, M. (1998). Medicine and surgery of South American camelids. Ames, Iowa:

Iowa State University Press.

Goyal S.M., Bouljihad M., Haugerud S., Ridpath J.F. (2002). “Isolation of bovine viral

diarrhea virus from an alpaca.” J Vet Diagn Ivest, 14(6), 523-5

Hoffman E. (2003). The complete alpaca book. Santa Cruz, California: Bonny Doon

Press.

Larson R. DVM, “A medical marvel.” Alpacas Magazine, Winter 1999, 122

Schwantje H., Stephen C. (2003) “Communicable Disease Risks to Wildlife From

Camelids in British Columbia.” [on-line]. Available:

http://wlapwww.gov.bc.ca/wld/documents/wldhealth/camelid_risk03.pdf

Wentz P.A., Belknap E.B., Brock K.V., Collins J.K., Pugh D.G. (2003). “Evaluation of

bovine viral diarrhea virus in New World camelids.” J Am Vet Med Assoc, 223 (2), 223-8

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Nancy Carr MD has alpaca farm A, Silver Cloud Alpacas, near Elginburg in eastern

Ontario, Canada. She would like to assure readers that her herd is now completely

healthy and not contagious, and in fact is one of the very few herds in North America

where all the cria have been tested to make sure they are not PI. She can be reached at

carralpacas@sympatico.ca or (613) 376-3389 or through her web site

www.silvercloudalpacas.com

Susy Carman DVM PhD is in Diagnostic Virology, Animal Health Laboratory,

Laboratory Services Division, University of Guelph, Box 3612, Guelph, Ontario, Canada

N1H 6R8. Email: scarman@lsd.uoguelph.ca. Phone: (519) 824-4120 ext. 54551

NEED TO KNOW

- BVD virus, a major problem in cattle, has now been shown to also cause illness,

abortions, and, most important of all, the persistently infected state in alpacas.

- If the alpaca is exposed to BVDV during early pregnancy she can produce a

persistently infected (PI) cria who sheds huge amounts of virus its whole life and

is the major source of the spread of BVD.

- The only way to be PI is to be born PI.

- Because a PI cria may not show any signs of illness for several months or longer,

the potential for BVD to spread between herds is significant because of the

practice of females with cria at side going to other farms for breeding.

- It is unknown yet how common BVD in alpacas is – this has the potential to have

a profound impact on the alpaca industry.

- All aborted or stillborn fetuses and unusually low birth weight or poor doing cria

should be tested specifically for BVDV, as there are usually no pathological

changes to suggest BVDV. Your veterinarian should consult with a veterinarian

virologist or lab that does BVDV testing about the appropriate tests to be ordered.

- Please copy this article for your veterinarian.

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Other articles about BVD may be found at:

http://www.claacanada.com/

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