Cache Valley Virus
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In the northeastern United States, a mosquito-borne virus known as Cache Valley virus can be a reason for reproductive losses.
HEADING INTO KIDDING season, every producer hopes for the best possible outcome with the fewest issues. We calculate due dates, stock emergency kits, and bed maternity pens. Running through the mental checklist of potential problems, we think of things like breech births, pregnancy toxemia, and colostrum. Rarely do we think of viruses.
In the northeastern United States, a mosquito-borne virus known as Cache Valley virus can be a reason for reproductive losses. While the occasional difficult kidding is considered run-of-the-mill for an experienced goat owner, it may be a reason to think twice and call the vet out to do disease testing.
Small ruminant practitioners in the northeastern states who have worked on Cache Valley cases report various experiences, from seemingly minor single incidents to more significant herd-wide patterns.
Warning: Graphic Pics Below
A pregnant doe becomes infected with the virus via mosquitoes, typically leaving the doe unaffected as the virus crosses the placenta and infects the developing fetus. The possible effects on the fetus depend on when the doe is infected. Does infected with this Orthobunyavirus in the first 32 days of pregnancy are more likely to experience abortions, which is when a fetus is delivered after its organs fully develop but before it’s able to thrive outside of pregnancy.
Should abortion occur early enough, it may simply go unnoticed by the doe and the farmer or assumed to be a year of poor fertility for that doe. If the infection occurs between 32 and 37 days of pregnancy, it’s more likely the doe will produce kids, either alive or stillborn, but with musculoskeletal or neurological defects.
Live kids may have deformed limbs (arthrogryposis), head and neck twisted in one direction (torticollis), abnormal curvature of the spine, or a poorly developed brain. After 37 days of pregnancy, the fetus may clear the viral infection without any noticeable repercussions.
Cache Valley Virus Doesn’t Always Present the Same Way.
Farmers who have experienced the virus on their farms describe various experiences. On a New York farm of 30 does, the breeding season began with a single fullterm stillbirth and one difficult delivery. However, by the end of kidding season, this farm saw 25% of their does deliver prematurely, and of these premature kids, 40% passed away soon after birth. Only two of those early kids presented with minor limb deformities.
On another New York farm of 20 does, several kids were born with limb deformities, and one was born missing an entire limb.
In herds ranging in size from 3 to 10 does throughout New England, one farm noted only a single stillbirth; another farm indicated that 100% of kids were born two weeks before their due date and eventually passed away. Another stated the majority of their does suffered silent miscarriages. Experts eventually determined Cache Valley to cause the losses in all these cases.
Where Does it Occur Most?
Most Cache Valley virus cases in the United States occur in the northeastern region, with fewer incidents along the Eastern shore of Maryland and Virginia. Whereas in Maryland and Virginia, Cache Valley activity appears to be related to saltwater mosquito habitats, in New England, research and surveillance indicate that Cache Valley activity seems to be unrelated to mosquito population density. Instead, the incidence of the virus appears dependent on how often the virus is evolving.
How Does the New England Strain Different from Others?
Cache Valley has the most rapid evolutionary patterns in New England compared to other regions of the United States. When a new viral strain enters the area, it will quickly disburse across that region and permeate vulnerable species populations. Once the population has been saturated with the latest viral strain, virus activity rapidly declines and ceases until a new strain evolves.
This pattern makes it difficult to predict Cache Valley activity in a particular area in any given year. Since no vaccine is available against this disease, exploring ways to prevent or identify it in your herd is essential. Breeding during vector season will present a higher risk for CVV, so depending on your production goals, you may want to change your seasonal management to breed outside of vector season.
Prevention
Those breeding in July and August, therefore subsequently kidding in December or January, will be more vulnerable to CVV than, for example, those breeding in November and kidding in April. Since this virus causes more devastating effects in naïve does (does who have never been exposed to the virus before) than in does that have previously had the virus, shifting your breeding season to avoid CVV exposure may only be a worthy strategy in naïve herds.
If your herd has already been affected by this virus, their immune systems may protect them from further infections. If you should find yourself amid kidding issues and wonder if CVV could be the cause, you may want to consider having your veterinarian out for diagnostic testing. It’s essential to understand how to catch the virus in action.
Diagnosing Cache Valley Virus
It sweeps from the dam to the fetus quickly and is typically no longer active during abortion. Therefore, diagnostics rely on identifying antibodies from fetal fluids, such as blood directly from the heart or the pleural space (the space between the lungs and the outer lining that encloses the lungs).
Therefore, to diagnose CVV as a cause of an abortion, you’ll want to save the fetus, refrain from dissecting it, and ship it out whole and promptly. If the kid in question is alive, but you still wish to test for CVV, you can use a blood sample, but they are most accurate if the blood is collected before colostrum is ingested.
While it sounds intimidating to hear your herd may be vulnerable to a virus that could cause anything from no signs to significant losses, simply being aware of prevalent diseases strengthens your growing knowledge base and empowers your decision-making during times of trouble. Understanding where a virus is, how it spreads, and what it may look like makes you a better advocate for your goats’ health.
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DR. ERIN MASUR, DVM, is a livestock veterinarian located in the northeast with a passion for small ruminant parasitology. On her own farm, she raises sheep, ducks, and children. You can keep up with her research at EarlyBirdWorm. com, or check out her services at SheepRockVet.com. For more frequent updates, you can find her on social media by searching for Sheep Rock Vet or Fork You Farms.
SOURCES:
- “Cache Valley Fever (CVF).” Cornell University College of Veterinary Medicine, 1 Mar. 2022, www.vet.cornell.edu/ animal-health-diagnostic-center/ news/cache-valley-fever-cvf.
- “Cache Valley Virus.” Cornell University College of Veterinary Medicine, 26 Feb. 2021, www. vet.cornell.edu/animal-healthdiagnostic- center/news/cachevalley- virus.
- “Confirmed Cases of Cache Valley Virus and Related Viruses at KSVDL.” Kansas State Veterinary Diagnostic Laboratory, Mar. 2020, www. ksvdl.org/resources/news/ diagnostic_insights/march2020/ confirmed-case-cvv-ksvdl.html.
- Lowry, Sarah. Interview. 21 June 2023. By Erin Masur. Telephone Interview.
- Pinn-Woodcock, Toby. “CVV.” Received by Erin Masur, 27 June 2023. Email Interview.
- Tuominen, Amy. Interview. 21 June 2023. By Erin Masur. Telephone Interview.
