Identifying and assessing large animal zoonoses

Shutterstock July 6 is World Zoonoses Day and now, more than ever, awareness of these diseases is vital. Zoonoses, as you know, are diseases that are able to pass between people and animals. Education and knowledge of such diseases are important for not just the practitioner’s and veterinary health care team’s overall wellbeing but also being able to impart such information to our clients should their pet or animal be diagnosed with a zoonotic disease. Approximately 61 percent of human pathogens are zoonotic, and approximately 75 percent of the emerging pathogens in the past decade have been believed to be zoonotic (I’m looking at you COVID-19). Unfortunately for us and our patients, interstate and international movement can allow for these pathogens to spread globally at rapid paces since animals and animal products, as well as people, are constantly crossing borders. Zoonoses are most commonly transmitted via direct contact, a bite or scratch, vectors such as ticks or mosquitos, exposure to bodily fluids, and inadvertent ingestion. While zoonoses occur from many domestic species, ones affecting livestock are of particular importance. The pathogens can not only cause issues to those directly involved in the care of livestock but in some cases the consumer of those agricultural products. Knowledge of large animal zoonoses can be instrumental in preventing a potential human health issue. Prevention The best prevention against zoonotic diseases is awareness. Client and staff education, as well as outreach in cases of outbreaks, is vital. Utilizing simple management techniques can make a huge difference in controlling the possibility of contracting a zoonoses. These include basic biosecurity, proper hygiene, and adequate handwashing. Being educated in regional zoonoses is also important as certain diseases are much more prevalent in specific areas. Lastly, reduction and eradication of ectoparasites can also decrease incidences, as well. While not a comprehensive list, this provides an overview for many of the most common livestock and large animal zoonoses veterinary professionals and the general public are most at risk of contracting. Brucellosis Brucellosis is caused by infection with the bacterium Brucella abortus and is also known as “contagious abortion,” “undulant fever,” or “Bang’s disease.” In cattle, the infection typically causes abortion and premature calving, usually between the fifth and eighth month of gestation. The pathogen has a propinquity for reproductive tissues and fluids. For cattle, infertility, reproductive issues, and abortions are frequent clinical signs. Bulls are also capable of transmitting the organism to cows during breeding. Milk from infected cows can also contain the pathogen. There is no treatment for Brucellosis, and prevention is the best measure by vaccination protocols. For humans, the biggest threat is exposure to contaminated reproductive fluids and remnants from birth. Prevention is best accomplished by wearing personal protective equipment (PPE) and handling infected animal tissues with gloves. In humans, the disease can also be known as undulant fever and can take two to six months after exposure for symptoms to occur. Clinical signs in humans: Flu-like symptoms such as headache, aches, fatigue, fever, and chills are most common. More chronic symptoms include intermittent fever, bone and joint infections, as well as reproductive problems such as abortion or premature birth and male reproductive tract issues. An acid fast stain of a Cryptosporidium parasite. Shutterstock Cryptosporidiosis Cryptosporidiosis, sometimes called crypto, is caused by the parasite Cryptosporidium parvum. It is a common and problematic parasite in young ruminants. Animals and humans are typically infected via contaminated water or food sources, as well as fomites; particularly those with fecal matter. In livestock, animals will exhibit water diarrhea, anorexia, and straining. Clinical signs in humans: Symptoms in humans are mostly gastrointestinal in nature and includes abdominal cramping, nausea, diarrhea, gas, and general malaise. They can appear anywhere from two to three days to two weeks after exposure. Prevention is best accomplished by meticulous hand washing after handling livestock particularly feces, washing fruits and vegetables that may have livestock fecal matter on it, and avoiding drinking water from questionable sources. West Nile West Nile is caused by a virus that can infect horses, humans, and birds. It is transmitted from the bite of the Culex species of mosquito that are infected with the virus. Mosquitos contract the virus when taking a blood meal after biting a wild bird that is also infected with the virus. Those mosquitoes are then able to transmit the virus to humans and other animals when biting to take a blood meal. Fortunately, the transmission of the virus does not always lead to clinical disease in both humans and animals. Humans are only capable of contracting the virus from the bite of an infected mosquito. The disease cannot be spread from person to person or from other animals to humans. Control and eradication of mosquitos by removing stagnant water sources and use of insect repellent is a formable preventive measure. A vaccination is available for equines. Clinical signs in humans: In most humans, clinical signs are mild and include fever and other flu-like symptoms. Approximately one in 150 humans will develop a more severe illness that can involve coma, seizures, paralysis, and vision loss. Severe disease and death usually is seen in geriatric, immunocompromised and those with comorbidities. Cutaneous anthrax lesion on a human. Shutterstock Anthrax This disease resulting from infection of the bacteria, Bacillus anthracis. Livestock will become infected by grazing in pastures that have affected soil; which becomes contaminated by decomposing carcasses. Often cattle will show no outward signs while living but may appear bloated with bloody discharge from orifices when found deceased. Clinical signs may include dyspnea, convulsions, and sudden death. Necropsies from animals suspected of anthrax death should be conducted with extreme caution. Acquisition of a blood sample from a superficial vein is sufficient to confirm diagnosis. Anthrax is a reportable disease, and a vaccine is available for cattle in areas with a high incidence. Clinical signs in humans: Humans contract anthrax in one of three ways: ingestion, inhalation, or skin contact. It can take up to a month to appear. Cutaneous anthrax appears as a clustering of small blisters or bumps that may itch. The blister will ulcerate and develop a black center. These ulcers most often appear on the arms, hands, face or neck. Inhalation anthrax presents initially with fever and chills and progresses to tightness in chest, dyspnea, coughing, headache, fatigue, general malaise, nausea, stomach cramps, and vomiting, Gastrointestinal anthrax clinical signs include fever and chills, bloody vomiting, nausea, bloody diarrhea, sore throat and painful swallowing, swelling around the neck and glands, headache, distention of the abdomen, and headache. Jaundice in a human from leptospirosis. Shutterstock Leptospirosis The most common strains of this bacteria causing the disease leptospirosis are Leptospira pomona or Leptospira hardjo. Often multiple abortions within a herd are the first clinical sign. Adult cattle may also exhibit jaundice and hematuria. Milk of affected females may also be yellow or blood tinged and thickened. The bacteria is transmitted to both animals and humans via direct contact with infected urine, placenta, or milk. Livestock can be vaccinated against the disease. Proper PPE and good hygiene can prevent infection. Humans usually contract the disease via direct contact with infected fluids. Clinical signs in humans: Fever, malaise, jaundice, and other flu-like symptoms. Tuberculosis Tuberculosis is caused by the pathogen Mycobacterium bovis. This is a reportable disease due to its zoonotic potential. It is spread to humans and other cattle via non-pasteurized milk, as well as direct contact. This can be from inhaling droplets expelled from infected lungs or ingesting contaminated feed. Cattle will exhibit a moist, soft cough with dyspnea, and tachypnea; increasing in severity as the animal reaches terminal stages. There is no vaccine available, and cattle are tested using a similar method used in humas by administering an intradermal test along the caudal tail fold. The incubation period in both cattle and humans can be several months to years before clinical signs develop. Prevention involves proper hygiene, PPE, and avoiding consumption of raw dairy products. Clinical signs in humans: Humans will present with mostly respiratory symptoms such as fever, chronic cough, and weight loss. They will also complain of overall general malaise. In rare instances, meningitis and meningoencephalitis can develop. This is usually fatal. An intradermal TB test on caudal tail fold in cattle. Shutterstock Q fever Coxiella burnetii is the causative agent for Q fever. It is an illness causing reproductive issues in goats, sheep or cattle,] as well as weak or stillborn offspring. (As an aside, the name comes from the original term, “query fever.”) Animals may be asymptomatic and contaminate fomites, water, and ground by passing the bacteria in their feces and infected reproductive fluids and tissues. Humans are exposed to the bacteria by direct contact and inhalation but also consuming raw dairy products, and contaminated food and water sources. The incubation period is between one to three weeks for livestock and two days to six weeks in humans. As with other zoonoses, prevention includes proper hygiene, PPE, and disinfecting areas exposed to aborted tissues. Clinical signs in humans: Flu-like symptoms, fever, general malaise, body aches, and chills are the most common clinical signs. Humans may also exhibit a cough, nausea, vomiting and diarrhea. Children may also have a rash. Contagious ecthyma, commonly known as ORF This is a cutaneous infection caused by a parapoxvirus. While most commonly observed in sheep and goats, humans can be infected by direct contact. Clinical signs in small ruminants include lesions around the mouth, nose, and teats. Lesions will become crusty over time. Neonates will then become exposed by nursing from affected teats. There is no treatment for the virus, but a vaccine is available. ORF is not typically fatal but dams may be reluctant to nurse offspring due to painful teats. The incubation period is three to seven days in goats and sheep. Humans handling affected animals should wear gloves and cover any open wound, as well as wash hands after handling. Clinical signs in humans: Humans who become infected will have a small, red cutaneous nodule that gradually will ulcerate and scab over. It is typically a self-limiting infection. ORF lesions on a human. Shutterstock Campylobacteriosis Campylobacteriosis is a bacterial disease caused by several strains of the Camplyobacter bacteria. Campylobacter jejuni, C. coli, and C. fetus are the most common. This disease is most prevalent in small ruminants, but other mammals are susceptible. The incubation period is between three to 25 days. Animals may be asymptomatic and pass the bacteria in reproductive tissues, and fluids and infected feces. Clinical signs when present are typically abortion and diarrhea. A vaccine is available but areas where fetuses were aborted should be disinfected. Humans should practice good hygiene, wear PPE, as well as avoid contaminated water, wash produce, and avoid raw dairy products. Incubation in humans is one to 10 days. Clinical signs in humans: Woman are at risk for reproductive problems including miscarriage, premature birth, and infants developing a fatal meningitis. Children and immunosuppressed are most at risk for gastrointestinal symptoms as well as fever, headache, diarrhea, and muscle pain. Erysipeloid cellulitis on a human. Shutterstock Erysipelas This is a disease of swine caused by the bacteria Erysipelothrix rhusiopathiae. Swine can develop symptoms that include a diamond-shaped rash on the skin. The bacteria can localize in the heart and joints, causing lameness and endocarditis. Swine can be vaccinated for the disease. Humans handling swine suspected of having erysipelas should cover open wounds, wear gloves, and practice good hygiene. Clinical signs in humans: The disease in humans is referred to as erysipeloid and usually manifests in one to seven days after exposure. They will have localized cellulitis which is extremely painful. The hands are the most common site of infection. Streptococcosis Streptococcosis caused by the bacteria Streptococcus suis is a common bacteria disease causing an acute and often fatal disease in young pigs. Neurological signs typically involve ataxia, blindness, tremors, fever, stiffened gait, and lateral recumbency. Prevention is best accomplished by wearing PPE and proper hygiene when handling sick animals. Clinical signs in humans: Humans contract the disease by direct contact with infected animals, and it typically takes anywhere from a few hours to three days for clinical signs to develop. Symptoms can be severe and include deafness, septicemia, meningitis, endocarditis, and toxic-shock syndrome. Milder clinical signs involve flu-like symptoms, general malaise, nausea, vomiting, and abdominal pain. Trichinella parasite in muscle tissue under the microscope. Shutterstock Trichinellosis Swine trichinellosis is a parasitic disease caused by Trichinella spp. of nematodes. Pigs are asymptomatic; however, the nematode will reside in the muscles. Humans then contract the disease by consuming undercooked pork products containing the parasite. To prevent infection in swine, avoid feeding undercooked or raw meat to pigs. Clinical signs in humans: Trichinellosis/trichinosis in humans will develop within about eight to 15 days after ingesting the nematode. Signs include nausea, vomiting, diarrhea, abdominal pain, fever, muscle pain, lethargy, and headache. Listeriosis Listeria monocytogenes is the most common causative agent for listeriosis, also known as circling disease or silage sickness. Oftentimes sheep are exposed to the bacteria via soil, and contaminated vegetation and silage. Younger animals are more susceptible to clinical issues and are infected by accidental ingestion of the bacteria. They will typically become septic and develop a fatal septicemia. Pregnant animals may also abort their fetuses. Adult animals usually develop encephalitis. Animals may commonly be asymptomatic and shed the organism via the intestines. Sheep and goats usually have a rapid and acute form of listeriosis with death occurring in as little as four to 48 hours. Cattle will often recover but with lasting brain damage. The organism is transmitted via fecal oral routes as well as fecal contamination of food and water sources. Humans become exposed to the disease via direct contact with sick animals but also contaminated food products. Prevention in humans involves meticulous washing of produce, thoroughly cooking meat products, and proper sanitation and hygiene. Clinical signs in humans: Listeriosis is most often problematic in infants and children, geriatrics, immunocompromised and pregnant women. Clinical signs typically manifests in encephalitis-type symptoms or septicemia. In pregnant women, there is risk to the unborn fetus; it can cause infection to the fetus, miscarriage, premature birth, or stillbirth. Listeria monocytogenes bacteria. Shutterstock Salmonellosis Salmonellosis is a bacterial infection involving the digestive tract. It is caused by the bacteria Salmonella enterica. Animals can exhibit no clinical signs and be asymptomatic carriers. They can also develop severe diarrhea with or without blood and mucus, fever, lethargy, and anorexia. Neonates can dehydrate quickly, and death can occur within two days. Animals are exposed when they consume contaminated food and water sources or from contaminated environment and fomites. The bacteria is shed in feces, saliva, nasal discharge, urine, and milk. Prevention is best accomplished by practicing good biosecurity, and sanitizing equipment and areas where infected animals reside. Humans should also drink only pasteurized milk since the bacteria can also be excreted in milk. Clinical signs in humans: Young children, immunocompromised, and geriatric adults are most at risk for disease. Common clinical signs are nausea, vomiting, fever, abdominal pain and cramping, and diarrhea. The clinical signs will manifest rapidly in humans and appear within eight to 48 hours of ingestion. Mycobacterium paratuberculosis or Johne’s disease (This last disease has not been classified as a zoonoses but deserves food for thought and warrants an honorable mention.) Mycobacterium paratuberculosis is the causative agent of Johne’s disease in cattle. The organism infects cattle by direct contact and accidental ingestion of fecal material from contaminated sources. Animals are slow to develop clinical signs, many taking years to develop. The diseases causes a slow progressive wasting of the animal despite normal food consumption. Some cattle may have diarrhea or no symptoms of disease while being asymptomatic shedders. Clinical signs in humans: Humans have not developed clinical signs; however, the organism has been discovered in the intestinal tract of those suffering from Crohn’s disease. This disease has many similar symptoms of paratuberculosis in cattle. It is believed it may be associated with Crohn’s disease but as of yet it is not determined if this agent causes disease in people. Conclusion Zoonotic diseases continue to invade our lives. Whether they are causing a global pandemic or wreaking havoc on our patients and clients, all members of the veterinary healthcare team should be aware of potential diseases and have the knowledge to prevent accidental infection. With new and emerging diseases, the possibility of unknown zoonotic hazards loom large, and it is up to all of us to be ready and willing to fight the fight. Jennifer Serling, CVT, RVT, VTES, BVSc, is a credentialed technician with more than 30 years of experience in both small and large animal practices. She has been a veterinary technician educator since 2007. She currently works for Appalachian State University as the Assistant Director of the Bachelors of Veterinary Technology program. Jennifer is a nationally known speaker as well as the author of several veterinary technology textbooks. She is the current President of the Association of Veterinary Technician Educators (AVTE). Jennifer resides in Tucson, AZ with her two boys: her cat and her favorite child, a golden retriever named Daffy. Resources USDA APHIS. Table of Contents. 2013. https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/nvap/NVAP-Reference-Guide Centers for Disease Control and Prevention. 2020; November 19. Symptoms of Anthrax. https://www.cdc.gov/anthrax/symptoms/index.html Zoonotic Diseases Resources and Prevention. (n.d.). CFSPH. https://www.cfsph.iastate.edu/zoonoses/ 2020; July 29. Zoonoses. World Health Organization. https://www.who.int/news-room/fact-sheets/detail/zoonoses Centers for Disease Control and Prevention. 2021; July 1. Zoonotic Diseases. Centers for Disease Control and Prevention. https://www.cdc.gov/onehealth/basics/zoonotic-diseases.html Merck Veterinary Manual. https://www.merckvetmanual.com Serling, J. (2021). Large animal medicine and nursing for veterinary technicians. Minneapolis, MN: Bluedoor Publishing. Thomson, S., Hamilton, C. A., Hope, et al. 2017. Bovine cryptosporidiosis: impact, host-parasite interaction and control strategies. Veterinary Research. 48(1). https://doi.org/10.1186/s13567-017-0447-0. Salmonellosis: Background, Management and Control. 2019; May 10. Cornell University College of Veterinary Medicine. https://www.vet.cornell.edu/animal-health-diagnostic-center/programs/nyschap/modules-documents/salmonellosis-background-management-and-control Listeriosis in Ruminants and Human Risk. 2006. Purdue.edu. https://www.addl.purdue.edu/newsletters/2005/fall/listeriosis.htm Zoonoses Associated with Cattle. Institutional Animal Care and Use Committee. Washington State University. (n.d.). https://iacuc.wsu.edu/zoonoses-associated-with-cattle/#:~:text=The%20diseases%20associated%20with%20cattle

Cookie	Duration	Description
cookielawinfo-checkbox-analytics	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Analytics".
cookielawinfo-checkbox-functional	11 months	The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional".
cookielawinfo-checkbox-necessary	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookies is used to store the user consent for the cookies in the category "Necessary".
cookielawinfo-checkbox-others	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other.
cookielawinfo-checkbox-performance	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Performance".
JSESSIONID	session	The JSESSIONID cookie is used by New Relic to store a session identifier so that New Relic can monitor session counts for an application.
viewed_cookie_policy	11 months	The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. It does not store any personal data.

Cookie	Duration	Description
vuid	2 years	Vimeo installs this cookie to collect tracking information by setting a unique ID to embed videos to the website.
_ga	2 years	The _ga cookie, installed by Google Analytics, calculates visitor, session and campaign data and also keeps track of site usage for the site's analytics report. The cookie stores information anonymously and assigns a randomly generated number to recognize unique visitors.
_gat	1 minute	This cookie is installed by Google Universal Analytics to restrain request rate and thus limit the collection of data on high traffic sites.
_gat_UA-	1 minute	A variation of the _gat cookie set by Google Analytics and Google Tag Manager to allow website owners to track visitor behaviour and measure site performance. The pattern element in the name contains the unique identity number of the account or website it relates to.
_gid	1 day	Installed by Google Analytics, _gid cookie stores information on how visitors use a website, while also creating an analytics report of the website's performance. Some of the data that are collected include the number of visitors, their source, and the pages they visit anonymously.
__gads	1 year 24 days	The __gads cookie, set by Google, is stored under DoubleClick domain and tracks the number of times users see an advert, measures the success of the campaign and calculates its revenue. This cookie can only be read from the domain they are set on and will not track any data while browsing through other sites.

Cookie	Duration	Description
ADV_u_id	3 months 8 days	Unique customer identifier used to track unique ad views and interactions with some ads.
anj	3 months	AppNexus sets the anj cookie that contains data stating whether a cookie ID is synced with partners.
fr	3 months	Facebook sets this cookie to show relevant advertisements to users by tracking user behaviour across the web, on sites that have Facebook pixel or Facebook social plugin.
IDE	1 year 24 days	Google DoubleClick IDE cookies are used to store information about how the user uses the website to present them with relevant ads and according to the user profile.
loc	never	AddThis sets this geolocation cookie to help understand the location of users who share the information.
OAGEO	session	OpenX sets this cookie to avoid the repeated display of the same ad.
OAID	1 year	Cookie set to record whether the user has opted out of the collection of information by the AdsWizz Service Cookies.
test_cookie	15 minutes	The test_cookie is set by doubleclick.net and is used to determine if the user's browser supports cookies.
uuid2	3 months	The uuid2 cookie is set by AppNexus and records information that helps in differentiating between devices and browsers. This information is used to pick out ads delivered by the platform and assess the ad performance and its attribute payment.
_fbp	3 months	This cookie is set by Facebook to display advertisements when either on Facebook or on a digital platform powered by Facebook advertising, after visiting the website.

Identifying and assessing large animal zoonoses

While rodents and birds are perhaps the biggest transmitters, several zoonotic diseases are passed through large animals.

Membership Required