Mosquito Borne Diseases in Goats
Reading Time: 4 minutes
The mosquito-borne diseases in goats fall into three categories: viruses, bacteria, and parasites. Learn about each and what to watch for.
-by Don Lewis There are roughly 3,500 species of mosquito on Earth. For most of us, that’s 3,500 too many. To be fair, many of these species don’t preferentially make a blood buffet of humans, and of those that do, blame the females of the species. But while itchy bumps caused by an allergic reaction to the mosquito saliva left behind at each feeding are bad enough, mosquitoes are a major vector for pathogens, such as viruses, bacteria, and parasites.
Although mosquito-borne pathogens cause more human deaths annually than any other animal, people aren’t the only ones suffering from these disease-transmitting scourges. Practically every member of the animal kingdom has one or more mosquito varieties that prey upon it … including goats.
Life Cycle of a Mosquito
After collecting a blood meal, the female mosquito lays her eggs in any available still water. If still water isn’t available, the female may lay eggs on soil or at the base of vegetation in areas susceptible to flooding. The eggs can survive for several months without being immersed in water but must be in water to continue the cycle.
The larvae hatch in water and feed on water-borne microorganisms. The larvae molt several times during this stage. Eventually, the larvae develop into pupae, which no longer feed but must remain in the water. Finally, an adult mosquito emerges and takes flight, leaving the water behind.
A mosquito’s life cycle typically takes a couple of weeks, but it may last for as long as a month in certain conditions. As a rule, mosquitoes don’t carry any pathogens during the egg, larval, or pupal stages of life, and any pathogens carried during the adult stage are acquired while feeding on an infected source.
Mosquito-Borne Diseases Affecting Goats
Like many others, goats are prey to hungry mosquitoes. These insects can be vectors of pathogens that cause illness in goats, other livestock, and occasionally humans. Some of these pathogens are present in the United States, while others haven’t made it here … yet.
The mosquito-borne pathogens that can infect goats fall into three categories: viruses, bacteria, and parasites. This article can’t list all mosquito-borne pathogens that can affect goats, and so I‘ll discuss only the most detrimental.
VIRUSES
• Cache Valley virus (Orthobunyavirus) — U.S.
Cache Valley virus (CVV) is endemic to many parts of the U.S. and can cause abortions, abnormal fetuses, and congenital abnormalities in goats. Currently, there are no available vaccines or treatments for the disease. Infected does don’t display symptoms of the disease. Rarely, humans have contracted CVV by mosquito bites, with the most serious infections leading to encephalitis and multi-organ failure.
In one herd study where CVV was present, insect control and a delayed breeding season relative to mosquito activity resulted in no further kid abnormalities over the two years following these steps.
• Rift Valley fever (Phlebovirus) — Africa.
First identified in 1931 in the Rift Valley of Kenya, Rift Valley fever (RVF) induces abortions in goats at a rate of nearly 100%. Spread by mosquitoes, the virus is zoonotic (meaning it can also infect humans). Since its original discovery, RVF has spread to most of Africa and Madagascar and, in a few cases, to Saudi Arabia and Yemen. An attenuated live virus vaccine has been developed for veterinary use and can provide long-term immunity but must not be used on pregnant animals.
• Wesselsbron virus (Flavivirus) — Africa.
A mosquito-borne virus that can cause high mortality (up to approximately 25%) among kids, as well as spontaneous abortions. Like RVF, the Wesselsbron virus is zoonotic and, in humans, causes headaches, muscle aches, and joint pain. Treatment of goats consists of immunization with an attenuated vaccine, often combined with the RVF vaccine.
BACTERIA
• Eperythrozoonosis (Mycoplasma ovis) — Worldwide. Eperythrozoonosis is a disease in sheep and goats caused by the bacterium Mycoplasma ovis. Mosquitoes are one of the known vectors. Goats infected with Eperythrozoonosis can suffer from anemia, jaundice, and (in rare cases) death. Older, previously infected animals develop immunity. No specific treatment is recommended, but the antibiotic oxytetracycline is occasionally prescribed.
PARASITES
• Goat malaria (Plasmodium caprae) — Africa/ East Asia. Mosquitoes are the primary vector for malaria parasites in all susceptible species. Goat malaria was first identified in Angola in 1923. Goat malaria isn’t considered to be zoonotic. Genetic studies of the parasite suggest the spread from Africa to Asia was related to domestic goat exportation.
Clinical signs of infection in goats are fever, pale mucous membranes, lymph node enlargement, and jaundice. Treatment for infected animals is mainly based on vector and parasite suppression and endectocide drugs, such as injectable Ivermectin and topical Fipronil.
• Setaria digitata — East Asia, India, Thailand. Setaria digitata is a species of parasitic roundworms that infect domesticated mammals, and can cause fatal cerebrospinal nematodiasis in cattle, goats, sheep, and horses. While S. digitata is most common in cattle, when mosquitoes introduce it to abnormal hosts like sheep or goats, the larval forms can migrate to the central nervous system, causing lumbar paralysis or “Kumari,” which can lead to death. Adult filarid worms can invade the eyes of livestock, causing blindness. Typical clinical treatments include DEC (diethylcarbamazine) or ivermectin.
The common factor in the pathogens outlined here is the delivery by mosquitoes. While many of these diseases have no effective clinical treatments, the most effective treatment is limiting animal and human contact with mosquitoes through environmental control of local still-water reservoirs and effective pesticide and repellent use.
SOURCES:
- Mosquito life cycle https://www.epa.gov/mosquitocontrol/mosquito-life-cycle
- Cash Valley Virus https://ksvdl.org/resources/news/diagnostic_insights/ march2020/confirmed-case-cvv-ksvdl.html https://www.vet.cornell.edu/animal-health-diagnosticcenter/ news/cache-valley-fever-cvf https://bvajournals.onlinelibrary.wiley.com/doi/10.1136/ vetreccr-2018-000725• Rift-valley-fever https://www.who.int/news-room/fact-sheets/detail/rift-valleyfever https://www.ncbi.nlm.nih.gov/pmc/articles/ PMC6316315/
- Wesselsbron virus https://www.sciencedirect.com/topics/agricultural-andbiological- sciences/wesselsbron-virus
- Eperythrozoonosis https://www.weeklytimesnow.com.au/agribusiness/ sheep-goat-health-epi-warning-after-perfectmosquito- breeding-conditions/news-story/ f18b5f3bc729b6af341cfc844e867f32 https://www.sciencedirect.com/topics/medicine-anddentistry/ eperythrozoonosis https://wormboss.com.au/other-occasional-parasites-ofsheep- and-goats/eperythrozoon/
- Goat malaria https://www.nature.com/articles/s41598-018-24048-0 https://parasitesandvectors.biomedcentral.com/ articles/10.1186/s13071-018-2872-y https://ejvs.journals.ekb.eg/article_123621.html https://pubmed.ncbi.nlm.nih.gov/27444556/ https://www.researchgate.net/publication/299342408_ Ungulate_malaria_parasites https://parasitesandvectors.biomedcentral.com/ articles/10.1186/s13071-021-04846-8 • Setaria digitata https://en.wikipedia.org/wiki/Setaria_(nematode) https://pubmed.ncbi.nlm.nih.gov/25924635/ https://www.merckmanuals.com/professional/infectiousdiseases/ nematodes-roundworms/overview-of-filarialnematode- infections https://www.sciencedirect.com/science/article/abs/pii/ S2405939018300935
Originally published in the 2024 Summer issue of Goat Journal and regularly vetted for accuracy.