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Recently there have been a lot of questions and concerns about the bovine disease known as Bovine Viral Diarrhea Virus (BVDV) among alpaca breeders across the country. This article comes from Dr. James Evermann at the Washington State University Department of Veterinary Clinical Services and the Washington Animal Disease Diagnostic Laboratory. It will hopefully give some insight into the disease and the diagnostic techniques that are currently being recommended for alpacas.
BOVINE VIRAL DIARRHEA
VIRUS IN CAMELIDS
(January 2006)
1. What is BVDV?
Bovine Viral Diarrhea Virus (BVDV) is one of several world-wide pestiviruses
known to infect domestic and wild ruminants, camelids and swine. For cattle
producers the virus causes economic losses through decreased weight gains,
decreased milk productions, reproductive losses, and death. As with most viral
infections, there is a wide range of clinical signs from in apparent infections
to diarrhea, respiratory tract infections, hemorrhage, abortions, congenital
defects, and death.
Acute Infection
Bovine viral diarrhea refers to a mild disease caused by a BVD virus infection
in immunocompetent cattle. In general, animals develop acute BVD 10-12 days
after infection. Since BVD infects white blood cells, whole blood (EDTA tube or
purple top tube (PTT)) is the sample of choice for isolation of BVDV from
clinically ill animals.
Persistent Infection (PI)
BVDV
can lead to a persistent infection in a calf/cria if it is infected during a
certain time in gestation. If infected prior to complete development of the
fetal immune system, the virus will not be recognized as a foreign pathogen.
After birth, the calf /cria will shed the virus and infect other animals in the
herd. Sometimes these calves look sick but they can also look perfectly healthy
thereby making it impossible to visually identify these animals.
2. Why is BVDV important
to my alpacas or llamas?
This
question cannot be completely answered at this time. There is much research
that needs to be performed to fully understand the implications of BVDV in
alpacas and llamas.
Research has shown that llamas and alpacas can be infected with the virus and
develop clinical signs. There have also been reports of suspected persistent
infections in crias. In cattle, persistent infected calves are the primary
source of spreading the infection to other animals. It is not known if
persistently infected crias are the primary source of herd infection in camelids,
but it is suspected. Alpacas and llamas are sent all over North America and
lapses in biosecurity could permit persistent infected cria to infect other
animals and herds.
3.
What are some concerns among
veterinarians and researcher regarding BVDV in alpacas and llamas?
A
few current questions among veterinarians and scientists requiring
investigation: Are there true persistent infections or longer transient
infections than seen in cattle? How accurately do the bovine-based tests
diagnose infections in camelids? Is there a new pestvirus specific to camelids
or a mutation of the BVD virus that appears to “prefer” camelids?
4.
What are some possible clinical
signs seen in alpacas and llamas?
Typical signs that a client may see include fever, oral ulcers, anorexia,
diarrhea, abortion, ill-thrift, and congenital defects.
5.
How is BVD transmitted?
The
most efficient method of BVD transmission in camelids is not known.
Transmission in cattle has been primarily by ingestion or inhalation of the
virus. The virus can be found in all body fluids (respiratory and oral
secretions, urine, milk, and semen) and feces. Transplacental (cow to fetus)
transmission also occurs. Transmission is assumed to be similar in other
susceptible species including alpacas and llamas.
6.
What species can transmit BVDV?
Virus can potentially spread between domestic ruminants (cattle, sheep, and
goats), camelids, and wildlife (deer, elk, etc).
7. Is there a vaccine
available for alpacas and llamas?
Currently there is no BVDV vaccine licensed for use in camelids. There are
several vaccines available for use in cattle. The vaccines do not prevent
infection but reduce the clinical disease effects. At this time, it is not
recommended to vaccinate camelids until more is understood about the virus.
Unwarranted vaccination can interfere with diagnostic testing and identifying
truly infected animals.
8.
Can BVDV infections be prevented?
No,
BVDV infections cannot be prevented but they can be reduced. Maintaining a
closed herd, implementing strict biosecurity protocols for all animals
(recommended not just for reducing BVDV infections), and periodic screening of
open herds can reduce the occurrence.
9.
What diagnostic techniques are
currently recommended for alpacas and llamas?
Types of Tests Available
·
Polymerase chain reaction (PCR) –
nucleic acid detection, very sensitive. Will detect persistent as well as
acute (transient) infections. Diagnostic method of choice because of excellent
sensitivity.
·
Antigen-enzyme-linked immunosorbent
essay (Ag-ELISA) –antigen detection; validation of this test has not been
established in camelids but is being evaluated.
·
Serology (serum neutralization) –
antibody detection, a single test indicates exposure, but not active
infection. Testing acute and convalescent samples and showing a 4-fold
increase in titer indicates active infection. False negatives may occur if
sample taken soon after an infection (prior to development of an immune
response), or in animals < 3 months of age when maternal, colostrums derived,
antibodies interfere with the test.
·
Skin biopsy with
immunohistochemistry (IHC) – antigen detection; results are not conclusive in
camelids.
·
Virus isolation – detects live
viruses in blood and tissues. May be required for virus typing.
Testing
Strategies:
Acute
Infection: BVDV acute infection can be diagnosed by virus isolation,
polymerase chain reaction (PCR) or serology. Virus detection must be done in
the first 3-10 days after the infection. A whole blood sample is the best
sample for BVDV detection by PCR or virus isolation. Paired acute and
convalescent samples collected 3-4 weeks apart are required to identify four
fold increases in serum antibody titers following recovery from clinical
illness.
Persistent Infection: Definitive diagnosis of persistent infection in
camelids cannot be based upon testing done at a single time point. Detection
of BVDV persistent infection requires showing virus is present in a particular
animal over time (the infection persists). Although the BVDV antigen ELISA test
done at a single time point is used to detect BVDV persistent infection in
cattle, whether or not similar interpretation of the test in camelids is
accurate is not known. Therefore, persistent infections in camelids should be
determined by detecting virus (by PCR or virus isolation) in sequential samples
collected 3-4 weeks apart.
The following testes are
recommended by the Washington Animal Disease Diagnostic Laboratory (WADDL) and
Washington State University Veterinary Teaching Hospital (WSU-VTH) for testing
alpacas and llamas. These are based on the most current information available
and may change as research is completed. Herds should be examined on a
case-by-case basis as testing may not be warranted in some situations.
1. HERD
SCREENING
- Submit whole blood samples
(PTT-purple top tube) (EDTA tube) for virus detection, and serum (RTT- red top
tube) for antibody detection individually marked to WADDL (or your local
accredited lab).
- WADDL will test PTT sample
for BVDV by PCR. Up to 10 samples can be pooled and tested, which may reduce
testing costs. Individual samples from positive pools would be retested to
identify individual positive animals within the pool.
- Negative results (BVDV
not detected) = no BVD infection.
- Positive results (BVDV
detected) = persistent OR transient BVD infection suspected.
- Definitive diagnosis
of persistent infection requires submission of another blood sample (PTT)
from an individual positive sample to be collected in 3-4 weeks and
re-tested.
- Serum samples (RTT) can be
used to check for BVDV antibody to determine prior exposure through serologic
testing if requested.
- If unable to test entire
herd, test all juveniles less than 2 years old and breeding males and
females. Again diagnosis of BVDV persistent infection would require 2 blood
samples collected 3-4 weeks apart.
2. NEW
ARRIVALS TO A HERD
- Quarantine for a minimum
of 30 days. Quarantining is not only important to allow screening for BVDV
but also for other diseases. Herd biosecurity is important to protect your
herd from disease new animals may bring with them. For animals that will be
remaining on your property a minimum 30-day quarantine is recommended before
introducing new animals to your herd.
- Negative results (BVDV
not detected) = no BVD infection.
- Positive results (BVDV
detected) = persistent OR transient BVD infection suspected.
- Remain in quarantine
until retested in 3-4 weeks.
- Negative re-test =
most likely a transient infection.
- Positive re-test =
persistent infection suspected.
A
negative-tested dam can be return ed to the herd , but recommended quarantining
just before delivery until newborn cria is tested with PCR and identified as BVD
infected or not.
3. OTHER
RECOMMENDED TESTS
- Necropsy and submit fixed
and fresh tissues to test all aborted and stillborn crias and crias or adults
with unexplained deaths. Submit whole blood (PTT) and serum (RTT) from the
respective dam as well.
- In addition to performing
an abortion screen it is a good opportunity to evaluate the herd’s trace
mineral status.
Ian Watt has a lifetime of experience and interest in Australian primary industries and has bred alpacas for 15 years, served as National President of the Australian Alpaca Association for four years after three years in other positions and is now an international alpaca consultant specializing in the teaching of breeding techniques to achieve superior fleece production. He is a graduate of Australia’s oldest agricultural college, has lectured at Roseworthy College, and spent six years in Papua New Guinea as a specialist animal production officer. While there he consulted with the World Bank, produced educational films and wrote his first book before moving back to Australia to open his own consultancy business. Ian is the editor and publisher of the “International Alpaca Handbook” and is currently well advanced in the writing of his fourth book, and second in alpacas, on alpaca fiber and its production. He lectures at workshops, seminars and speaking engagements around the USA and lives in Morro Bay, California.
ALPACAS FOR ME – fact v fiction
By Ian Watt
Alpacas are not for everyone – fact.
Welcome to the wonderful world of alpacas – a world that will give you hours, days and years of absolute pleasure and joy… and moments of frustration, sadness and worry.
While there is much to enjoy and appreciate about these wonderful animals, they are an animal that can totally consume you and your life or they can give you measured happiness and satisfaction that only animals seem to be able to give human beings.
Once we accept ownership of any animal we accepts custodianship of a life and the responsibility that comes with that custodianship – a responsibility that most of us accept with alacrity and purpose. However, we can only do that when we have sufficient knowledge and understanding to make a considered decision.
Hopefully this paper will give some reassurance where needed, identify potential pitfalls in alpaca ownership whilst also filling in some gaps that may appear through conflicting information.
Firstly, let it be quite clear that this discussion comes from the perspective that alpacas are animals and not extensions of human families and/or values.
Secondly, the information comes from a personal perspective based on years of both ownership as well as industry development and private consultancy in commercial aspects of fibre and animal production.
And, lastly, it is one persons’ opinion!
Huacaya and Suri are two different breeds.
Fiction – they are both alpacas with differing fleece qualities. For as many times that temperament, bone density, head profile, etc are promoted as breed differences, as many examples of compatability in those same traits that can be found. Crossing these fleece types wil always produce either an huacaya or a suri fleece type and the animal will always be an alpaca.
Alpacas are environmentally friendly.
True – and this is a BIG feature of owning these animals! The grazing nature of alpacas together with their padded feet, poo pile practices, ability to do well under harsh environments and lack of need of high quality pastures are all features that should endear these animals to conservationists and environmentalists alike. Most domesticated farm animals damage the environment in one way or another – these animals do not unless they are unsympathetically managed to disadvantage. Browsers by nature, they rarely decimate areas of paddocks, their padded feet do not tear at the soil structure creating potential erosion problems, their poo piles limit pollution of the pasture on a large scale and limit the spread of internal parasites, and their ability to process poor quality grasses limit the need for provision of improved pastures through the use of chemical fertilizers, pesticides and weedicides.
Alpacas need specialist fencing.
True - and false. Fencing is usually associated with keeping animals within specified boundaries for either legal, social or management purposes. In America there is an added complication in keeping alpacas and that is to deter predators from entering the property and creating untold havoc and pain. Bears, cats, deer, coyotes and cats are examples of environments where standard four foot fencing would be inadequate and where higher, closer spaced wire and reinforced posts will be necessary. For those areas that do not have these predator risks, standard seven wire fencing with a barb along the ground and the top wire four feet above the ground level will suffice.
Alpacas produce a cria once a year.
False – and probably one of the most quoted and inaccurate myths about these animals. Alpacas have a pregnancy gestation of 11.5 months on average with periods ranging from 11 to 12 months not uncommon. Depending on personal preference and environmental considerations (snow, cold, heat, humidity for example), birthed females may be mated as early as 10 to 12 days after delivery or as long as three months. On average, a hundred females will produce and wean about 70 cria a year up to 80 with good management practices.
Females should not be mated under 18 months to two years.
False – ideally a female alpaca should weigh a hundred pounds and be well grown and fertile before mating. Under-developed and underweight animals should never be mated regardless of age. There are some breeders who believe that other considerations such as social maturity should be considered.
Alpacas need shelter.
True - most animals benefit from shelter and alpacas are no exception. Shelter from wind and rain is essential for younger animals especially newborn. Shade from the sun is essential for pregnant dams as excessive heat can form deformities in the unborn and place enormous stress on the cooling system of the dam.
Alpacas are camels and do not need much water.
False – while alpacas are members of the same family as camels, they need as much water as any other specie of farm animal. Clean, fresh and plentiful water is essential for healthy alpacas.
Alpacas need teeth and feet trimming.
True – especially where they are run under ‘improved’ growing conditions (‘improved’ is where pastures have been upgraded, soils are damp and stone free and animals have an easy time of it). Foot trimming once or twice a year is normal practice whilst teeth may need to be trimmed annually depending on the type of feed being fed. Both operations can be done on farm by the owner and are not difficult.
Cria are high maintenance.
False – by far the large majority of cria need minimal maintenance and care. These are very hardy animals that usually need minimum human intervention to survive and do well. It is humans who ‘see’ a need for intervention that create (no pun intended!) situations and fears that require help. A careful eye at birthing, treatment of the umbilical cord with an iodine compound and checking to ensure that the airway is clear is all that is usually needed at birth. Close scrutiny to ensure that the cria is getting essential colostreum in the first 24 to 48 hours and adequate milk supply in the following weeks should be normal management practice. Of course, there will be occasions when intervention for more serious reasons will be essential but these are not frequent.
Alpacas spit and kick.
True – these are natural defence reflexes that are not usually aimed at humans but are often hurtful or embarrassing when they are!
Alpaca fibre is seven times warmer than wool.
False – alpaca fibre is thought to be as much as three times warmer than the same weight of wool which makes it a highly sought after knitting alternative to wool. There is much made about the supposed hollowness of alpaca fibre but the reality is that there is not much hollow fibre but there are other features which make alpaca such a desirable alternative.
Natural coloured alpaca fibre does not fade.
True – as with all naturally occurring colours in fibre, they will not fade thus giving alpaca a unique place in natural fibres.
Breeding like colour to like colour will give like colour.
False – while breeding to this recipe enhances the chances of a predictable colour outcome, the fact is that breeding for colour is still something of a crapshoot. Breeding like to like will, in most cases, enhance the chances of a specific colour outcome but not guarantee it.
Commercially, the fibre processors want white colour.
True – the international demand is for white fibre. Colour enjoys a unique niche market but in a commercial sense it will be many, many years before there are sufficient quantities of any one colour to justify commercial processing runs.
Spinners and weavers are looking for colour fibre.
True – this market is huge and must be unsatisfied at this time. However, it is a niche market that requires much more individual effort to discover and encourage.
Alpacas in America are a sustainable industry.
True – there are many advantages America has to sustain a large alpaca industry including population, land, wealth and lifestyle. Enthusiasm for all things alpaca remains unabated with record numbers joining the industry marketing body, AOBA, record auction sale clearances – and prices sometimes – strong farm gate sales and keen consumer interest in fibre products. As the national herd grows there will be a separating of prices based on quality with lesser quality animals becoming more and more affordable. The future looks really bright and more-or-less assured with the usual caveat that buyers should do their research really well before entering what is still essentially a risk industry.
Never before has so much information about alpacas been available to new entrants (or existing stakeholders for that matter) and not for a long time have so many Americans been open to lifestyle changes that these animals can bring.
As with all things, investing money in lifestyle brings about its own set of issues that need to be researched, considered and acted upon.
Alpacas are no exception.
When considering these wonderful animals, look beyond the hype and glossy marketing material, ask the questions and research the responses. Only then can you make the investment confident in the outcomes as you enjoy these animals and your involvement in the supportive and caring world of alpaca owners and breeders.
*Ian Watt is the principal of Alpaca Consulting USA and Elite Alpaca Breeding Systems, an independent specialist consulting company based in Morro Bay, California.
He is also Editor and Publisher of ‘The International Alpaca Handbook” and conducts education and training seminars/workshops on fibre appreciation and breeding programs.
Elite Alpaca Breeding Services
Alpaca Consulting Services
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