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Zoonotic diseases are diseases that can be transmitted from animals to humans. Information and updated news can be found at the following website: http://www.cdc.gov/nczved/ (Center for Disease Control, National Center for Zoonotic, Vector-Borne and Enteric Diseases). The following are diseases that are present in the United States. There are a number of exotic and foreign animal diseases that are zoonoses as well, but have either been eradicated or were never present in the United States. Anthrax (also known as charbon, malignant pustule, malignant carbuncle, splenic fever, woolsorter's disease) Anthrax is caused by the bacterium Bacillus anthracis, a spore-forming, encapsulated, Gram-positive rod-shaped bacterium. Herbivores are the primary hosts of this bacterium, whereas humans and other mammals are considered incidental hosts. The route of transmission is oral, respiratory or cutaneous. Animals usually ingest contaminated soil. Humans may be exposed via open wound on the skin of affected animals or animal products, via inhallation of spores and possibly fly bites. The incubation period varies from 1-20 days. Signs develop due to the productio of toxin by the bacteria, resulting in sudden death most commonly. Other signs that may be observed include fever, disorientation, collapse, muscle tremors, difficulty breathing, and terminal convulsions. In horses, additional signs may include colic. Death usuallly occurs in 1-3 days. Unclotted blood is highly suspicious of anthrax. Laboratory diagnosis includes microbiological culture and sensitiivty. Due to the possible inhalation of bacterial spores, necropsy on animals suspected of anthrax is not recommended. If a case is suspected, notification of state and/or federal veterinarians is required. The organism can be killed with a 5-10% formaldehyde solution. Vaccination of susceptible animals may be necessary. Carcasses should be burned. In humans, the cutaneous (skin) form is most common, appearing initially as a pimple and progressing to an eschar (ulcerated dry black scab). Without antibiotic treatment, 10-20% of human skin cases may be potentially fatal. http://emergency.cdc.gov/agent/anthrax/ Botulism (also known as shaker foal syndrome, toxoinfectious botulism, loin disease, bulbar paralysis) Botulism is caused by the bacterium Clostridium botulinum, a spore-forming, anaerobic bacterium with produces a potent neurotoxin. Seven types of toxin are known, classified as types A through G. Types A, B, E and F cause disease in humans. Type C is the most common type seen in animals. Type D is seen occasional in cattle, with type B occuring in horses. May species of mammals and fish may be affected by botulism. The bacteria, although present in the soil, can only grow under anaerobic (no oxygen) conditions. Botulism usually occurs when animals or humans ingest preformed toxins in foods or the bacteria spores germinate in anaerobic tissues and produce toxins as they grow. Performed toxins may be found in the following: grass, hay, grain, spoiled silage, carcasses, canned foods. The incubation period ranges from 2 hours to 2 weeks. The disease is characterized by progressive, flaccid motor paralysis. Initial signs include difficulty chewing and swallowing and generalized weakness. Death is due to paralysis of the respiratory or cardiac muscles. In cattle and adult horses, signs include drooling, restlesness, incoordination, urine retention, dysphagia (inability to chew/swallow), with progression to sternal and lateral recumbency. In foals less that 4 weeks of age, shaker foal syndrome may be seen. Signs include a stilted gait, muscle tremors and inability to stand for more than a few minutes. This disease is typically difficult to diagnose with laboratory tests, as the toxin is not always found in the feed or clinical samples at the time of presentation. Quarantine is not necessary. It is important to realize that this disease cannot be transmitted from animals to humans. The public health concern is present with inadequate heating during canning or food preparation, wound contamination with inadequate cleansing, and intestinal botulism in children less than a year old due to spores present in foods (honey being the most well known source). The case fatality rate in foodborne cases is 5-10% and in infant botulism less than 1%. http://emergency.cdc.gov/agent/botulism/ Bovine Spongiform Encephalopathy or BSE (Mad Cow Disease) BSE is a transmissible spongiform encephalopathy (TSE) affecting cattle. TSEs are progressive and fatal neurodegenerative diseases. The causative agents are throught to be prions, proteinaceous infective particles smaller than any known virus. This agent is extremely resistant to any treatments that normally destroy bacteria, viruses and fungi. The first case of BSE was diagnosed in the United Kingdom in 1986, with 3 cases identified in the United States. The first case was a mature Holstein in Washington state on 12/23/03, imported from Canada; the second case was a mature Brahma x cow in Texas on 6/24/05(the first endemic case in the US) and the third was a mature cow in Alabama on 3/15/06 (undetermined herd of origin). BSE appears to be transmitted orally, with the agent found mainly in nervous tissues. The incubation period ranges from months to years, with a peak incidence affecting cattle 4-5 years of age. Signs progess slowly and affect the neurologic system: hyperesthesia (sensitivity to touch), hindlimb ataxia, pelvic swaying, hypermetria, termors, falling and behavioral changes. Death occurs weeks to months after the onset of signs. BSE is always fatal. BSE is identified by detecting PrPsc (a disease-specific isoform of the membrane protein PrP) in the central nervous system. If this disease is suspected, it is recommended that the state and federal veterinarians be contacted immediately. The whole herd is quarantined and trace backs occur. Sodium hypochlorite and sodium hydroxide are effective chemical disinfectants. The public health concern is due to the ingestion of BSE contamined food products and the development of variant Creutzreld-Jakob disease (vCJD). vCJD has been found to affect primarily young people; there is no known treatment. http://www.cdc.gov/ncidod/dvrd/bse/ Bovine Tuberculosis Bovine TB is caused by Mycobacterium bovis, a gram-postive, acid-fast bacterium. Most commonly present in less developed countries, this disease is a significant zoonosis that is spread to humans through aerosols and the ingestion of raw milk. Cattle and buffalo are the maintenance hosts, with infections described in a large number of other domestic and wild mammals. The clinical signs may take months to develop; infections may remain dormant for years and reactive during stress or old age. The disease is usually chronic and debilitating, with progressive emaciation, a low-grade fluctuating fever, weakness and innapetance. Pulmonary and gastrointestinal signs include moist coughing, increased respiratory rate and effort, enlarged lypmph nodes, diarrhea and constipation. Necropsy reveals the presence of granulomas. Laboratory tests in live cattle include the tuberculin skin test, as well as several recent blood tests. Humans ususally ingest the bacteria through raw milk and other dairy products; inhalation of the bacteria can also occur. http://www.cdc.gov/tb/default.htm Brucellosis (malta fever, mediterranean fever, undulant fever, enzootic abortion, contagious abortion, Bang's disease) Brucellosis is caused by several bacterial species: Brucella abortus, B. melitensis, B. suis, B. canis, B. ovis and B. neotomae. The organism is a gram-negative coccobacillus or a short rod. B. abortus causes disease in cattle, bison and water buffalo. B. melitensis affects primarily sheep and goats. B. suis affect pigs and B. ovis affects sheep. Horses in contact with infected cows can develop fistulous withers or poll evil, most commonly caused by B. abortus. Brucellosis is usually well controlled in developed countries. Transmission is via the placenta, fetus, fetal fluids and vaginal discharge from infection animals. Bacteria are found in urine, blood, milk and semen; shedding in milk and semen may be prolonged or lifelong. Infection occurs through ingestion or contact through mucous membranes and skin. The incubation period ranges from 2 weeks to 5 months in cattle. Clinical signs include abortions, stillbriths, weak calves in cattle; abortion, retained placenta, epididymitis and orchitis in goats and sheep; abortion in pigs and fistulous withers and poll evil in horses. Definitive diagnosis relies on culture and identification of the organism. Serological screening tests can be performed in cattle, shppe and goats. Suspected cases of brucellosis require notification of the state and federal veterinarian. Brucellosis is highly pathogenic in humans and is easily acquired. The disease includes influenza-like signs that may occur for several days up to a year or longer. The case fatality rate is less than 2%, usually due to endocarditis. http://emergency.cdc.gov/agent/brucellosis/ Campylobacter Campylobacteriosis is caused by Campylobacter jejuni or Campylobacter coli, with C jejuni accounting for 90% of confirmed human infections. C jejuni and C coli exist as commensal organisms in poultry and livestock but are considered human pathogens. C jejuni in poultry occurs most commonly in broiler flocks during the production cycle, with horizontal transmission (from bird to bird) an important method of spread within a flock. Campylobacter often inhabits the intestinal tract of calves and sheep, most commonly C jejuni isolates. In swine, C coli is the predominant species. In humans, symptoms of campylobacteriosis range from diarrhea to dysentery. Self-limited acute diarrhea is most commonly noted. However, approximately 100 people, mostly infants, elderly or immunosuppressed individuals, die of C jejuni infections each year. Some sequelae of infection include Guillain-Barré syndrome, an immune-mediated disorder of the peripheral nervous system causing flaccid paralysis and reactive arthritis (Reiter's syndrome). Disease prevention relies on reducint pathogens loads at the fram, improving carcass processing, promoting safe food-handling practices and handwashing after animal contact are methods to reduce the risk of exposure to Campylobacter. http://www.cdc.gov/healthypets/diseases/campylobacteriosis.htm Clostridium difficile http://www.cdc.gov/ncidod/dhqp/id_CdiffFAQ_general.html Cryptosporidiosis Cryptospordiosis is caused by coccidian parasites of the genus Cryptosporidium and are smaller than other coccidia seen in animals. Cryptosporidium parvum is usually the species implication in animal and human infections. The method of transmission is direct, via fecal-oral route or via contaminated food, water or fomites. Cryptospordium oocysts differ from other coccidia in that they are infectious at the time of excretion and may excyst in the intestine prior to being excreted in the feces. The infection persists until the immune system of the host clears the parasite. The organism invades the apical surface of intestinal epithelial cells. These are considered primary pathogens, causing lesions in the small and large intestinal tract and diarrhea. Cryptosporidia are prevalent in neonates of ruminant species and are ubiquitous in the intestinal tract of beef and dairy calves. Most calves are infected before 6 weeks of age, with 25% of calves with diarrhea aged 5 days to 1 month infected with C parvum. Unlike cattle, human beings of all age are susceptible. Treatment for all species is supportive, as no antibiotic has proven effective against the organism. Prevention of disease relies on minimizes fecal-oral transmission between calves and between calves and humans. Management practices on the farm are key to maintaining a clean environment for calves. Using good sanitation and hygiene practices when handling calves will reduce the risk of developing cryptosporidiosis. Chemical disinfectants are generally ineffective. Most people infected with C parvum develop immunity and recover from infection as long as their immune system is normal. http://www.cdc.gov/crypto/ Eastern Equine Encephalomyelitis or EEE EEE is caused by an Alphavirus of the Togaviridae family. The virus is a single-stranded RNA arbovirus. Western and Venezuelan EE do not typically affect horses in this part of the country. However, travel to western and central USA, Canada and South and Central America may put you or your horse at risk of these viruses. These viruses can infect rodents, birds, humans and equids. Transmission is via the saliva of mosquitoes that have been previously feeding on viremic animals. Disease transmission is seasonal and dependent on warm temperatures and standing water, promoting mosquito reproduction and development. EEE viruses cycle between birds and mosquitoes. Humans and horses are dead-end hosts and do not have a viral load in the blood that mosquitoes can pick up and transmit to other mammals or birds. The incubation period ranges from 5-15 days. Signs include fever, anorexia, depression, behavioral change, ataxia, blindness and progressive loss of motor control. The mortality rate for EEE is 70%. Virus isolation and identification and paired serology are used for identification. Transmiision is dependent on the mosquito vector; control and use of mosquito repellants and screens are effective in reducing the incidence of disease in horses and humans. A variety of vaccinations are available in horses; the frequency of adminstration is dependent on the risk of exposure. In Georgia, booster vaccinations are recommended at least every 6 months. In humans, flu-like symptoms are observed, with progression to neurologic disease. EEE in humans has a mortality rate of 65%. http://www.cdc.gov/ncidod/dvbid/westnile/conf/26thbiennialVectorControl/pdf/state/Georgia.pdf http://www.cdc.gov/ncidod/dvbid/arbor/eeefact.htm Escherichia coli O157:H7 E coli is a coliform, rod-shaped bacterium that is present in feces of normal animals. The most pathogenic type of E coli in humans is serotype O157:H7, known as enterohemorrhagic E coli (EHEC). Cattle are considered the major source of EHEC, with cattle feces being the principal source of E coli O157:H7 problems. EHEC is responsible for approximately 62,500 cases of foodborne disease annually in the US, with approximately 52 deaths annually. Deaths are most commonly due to hemolytic uremic syndrome (HUS), resulting in kidney failure in children. Although cattle are important sources, the bacteria are rarely associated with clinical disease in cattle. E coli O157:H7 is considered a transient member of the normal flora of cattle, with animals shedding the bacteria from a few days to a year. Warm weather correlates with an increase in rates of fecal shedding. The pathogenesis of EHEC is due to the presence of Shiga toxin (Stx) genes, locus for enterocyte effacement (LEE) and a hemolysin. These 3 virulence factors are present in most E coli associated with bloody diarrhea and HUS in humans. The LEE is responsible for the attachment of the bacteria to the membrane of the enterocyte (cell in the small intestinal tract) and distruction of the microvilli (small thin projections from the cell of the intestinal tract responsible for absorption of nutrients). The virulence factor hemolysin is responsible for creating pores (small openings) at the surface of the intestine. Shiga toxins affect primarily intestinal lining cells and kidney lining cells, and are thought to be the major factor contributing to HUS. Strategies to prevent the exposure and spread of EHEC relies on managemenet practices on the farm and during food preparation and processing. Cattle and sheep feces are sources for contamination of food products and water sources. Undercooked beef products, unpasteurized milk and dairy products and contaminated water are potential sources of infection for humans. http://www.cdc.gov/ecoli/ Leptospirosis Leptospirosis is a bacterial disease caused by the spirochete Leptospira interrogans, in which a variety of serovars, or strains, are present and adapted to different species of animals. There are 184 serovars worldwide belonging to 20 serogroups. The most important serovars in North America are autumnalis, hardjo, pomona, canicola, grippotyphosa and icterohemorrhagiae. Leptospirosis can affect a wide variety of animals, including humans. In the veterinary field, the most common sources of leptospirosis are cattle and dogs. However, deer, sheep and other wildlife can also carry the organism. The bacterium is transmitted in the urine of an affected animal, with contamination of water sources being a common source of disease for humans. Direct contact with urine from an affected animal is also a potential source of contamination. Contamination may also occur via spread of bodily fluids from affected animals. The incubation period in animals ranges from 2 to 20 days. Signs of leptospirosis in animals include abortion in cattle (adult cattle rarely die from the disease), liver and kidney failure in dogs, and possible recurrent uveitis in horses. In humans, a wide range of symptoms may be observed, with some individuals showing no signs of disease. Meningitis, liver disease and kidney failure result if undiagnosed and untreated. The incubation period in humans ranges from 4 to 14 days. The organism is initially confined to the blood stream and may be diagnosed on blood culture, prior to moving to the kidneys, at which time the organism may be identified in urine. Diagnosis relies on identifying the organism in the blood or urine or obtaining serological titers to the organism in question; several serovars should be tested at that time. Treatment relies on killing the organism and treating any potential complications due to the disease process. In dogs, penicillin is used to eliminate the organism during the blood infection phase and doxycycline used to eliminate the carrier phase. For animals at risk of developing leptospirosis, vaccination against the most common serovars is highly recommended. http://www.cdc.gov/ncidod/dbmd/diseaseinfo/leptospirosis_g_pet.htm Listeriosis http://www.cdc.gov/nczved/dfbmd/disease_listing/listeriosis_gi.html Orf http://www.cdc.gov/ncidod/dvrd/orf_virus/ Q Fever Coxiella burnetii is a gram-negative coccobacillus responsible for causing Q (Query) fever, a disease first identified in Queensland, Australia. The organism lives and replicates in host monocytes and macrophages (types of white blood cells). The agent is commonly transmitted to humans from direct contact with reproductive tissues of cattle, sheep and goats. Aerosol transmission via the inhalation of contaminated materials is also a potential source of infection. Coxiella burnetii has 2 distinct life cycle stages: a vegetative form known as the large-cell variant (LCV) and the infectious form known as the small cell variant (SCV). In the host, the organism has an affinity for the placenta and is shed in fetal fluids and membranes, milk, urine, feces and in fine-particle aerosols. The organism is able to persist in the environment for weeks to months and transmission requires an extremely low infectious dose. Sheep, cattle and goats are the most common livestock reservoirs of Coxiella burnetii, with cats and dogs also susceptible to infection. The organism may be transmitted among animals via tick bite as well. In ruminants, Q fever occasionally results in abortion, stillbirths and dystocia (complicated deliveries). Among humans, the signs of Q fever are broad. The incubation period ranges from 1 to 3 weeks. The acute disease may include fever, headache, muscle aches and cough. Other signs may include fatigue, rigors, night sweats, nausea or vomiting. Chronic infection may occur in 1-2% of patients acutely infected with C burnetii. One of the most common long-term complications is endocarditis, which may be life threatening. Laboratory diagnosis of Q fever relies on laboratory diagnosis due to nonspecific signs. The risk for transmission can be reduced through proper sanitation when dealing with birthing animals and ensuring proper pasteurization of milk products. http://www.cdc.gov/ncidod/dvrd/qfever/index.htm Rabies Rabies is a fatal central nervous system disease affecting all mammals and is an important zoonotic disease in humans, resulting in more than 55,000 people dying of this disease worldwide every year. Rabies results from infection by the rabies virus, Lyssavirus, in the family Rhabdoviridae. All warm-blooded animals may be affected. The major reservoir hosts are skunks, weasels, stoats, martens, dogs, wolves, jackals, raccoons, mongooses, meerkats and bats. Rabies in endemic in the wildlife in Georgia. The disease is spread by wound or mucous membrane contamination with saliva. Most commonly, the disease is transmitted via the bite of an infected animal, but may occur due to infected saliva contacting a wound or abrasion on the skin, oral transmission, respiratory transmission or organ transplants if the donor was infected. The incubation period varies depending on the species, from weeks to months. Rabies results in central nervous system signs, such as paralysis, behavioral changes, ataxia, altered voice, inability to swallow, distress and aggression. The clinic course is divided into 3 phases: - prodromal: 1-3 days duration, vague but increasing neurologic signs
- excitative: the furious form is accompanied by extreme aggression and unpredictable behavior, incoordination, seizures and death
- paralytic: minimal behavioral changes with paralysis of the throat and jaw muscles, coma and death
Death usually occurs within 10 days of the appearance of clinical signs. Rabies vaccines are effective and available for dogs, cats, ferrets, horses, cattle, sheep and humans. Laboratory diagnosis requires the submission of brain tissue and identification of the virus. State and federal authorities should be contacted if the disease is suspected. Animals with suspected rabies should be destroyed and the brain submitted for rabies testing. Unvaccinated animals that have been exposed should be euthanized immediately or quarantined. Exposed animals up to date on rabies vaccination should be revaccinated and monitored closely for a minimum of 45 days (this period varies from state to state). http://www.cdc.gov/rabies/ Ringworm http://www.cdc.gov/healthypets/diseases/ringworm.htm Salmonella Salmonellosis is caused by gram-negative bacterium Salmonella. There are currently 6 subgroups within the genus, with salm0nellae belonging to a single species, S enterica. Salmonella subgroup I includes obligate parasites and pathogens of warm-blooded animals, most often associated with human and domestic animal disease. There are some 2,000 Salmonella serovars, resulting in increased time and expense of diagnosis. There are 4 major groups: B, C, D and E. All Salmonella infections, with the exception of S typhi and paratyphi A and C, are considered zooonoses. Human and animal infections usually occur secondary to oral consumption of feces or feedstuffs ontaining Salmonella organisms. Overstocking of animals is considered a risk for the development of salmonellosis. In humans, most infections results from the consumption of contamination food, most commonly pork, beef, poultry, eggs and milk products. Vegetables grown in soils fertilizing with feces containing Salmonella are also a potential source of infection. It has been estimated that 2-4 million Americans are infected yearly with Salmonella. Clinical signs of Salmonella include septicemia, acute enteritis and chronic enteritis. In horses, signs include depression, high fever, +/- diarrhea, and possible death. Some forms of salmonellosis occur secondary to concurrent disease, changes in physiologic states and stress due to transport, housing changes or surgery. A chronic carrier state is identified in which a clinically normal individual sheds the organism for weeks to months. In humans, clinical salmonellosis is characterized by sudden fever, muscle aches, abdominal cramps, nausea, vomiting and diarrhea. Salmonella is difficult to control due to its ability to survive in the environment and in animal carrier hosts. Salmonella is sensitive to heating and drying; however, the bacterium can remain viable on pasture in feces and in soil for up to 7 months. Identification of carrier animals is difficult as they may shed organisms periodically. Reducing the risk of disease caused by Salmonella requires eliminating exposure to feces possibly containing the organism, effectively pasteurizing milk, cooking eggs and egg products, as well as cooking and storing food products appropriately. http://www.cdc.gov/salmonella/ Streptococcus suis http://www.cdc.gov/eid/content/14/1/183.htm Vesicular Stomatitis Vesicular stomatitis (VS) is caused by vesicular stomatitis virus, a member of the genus Vesiculovirus in the family Rhabdoviridae. It is a large bullet-shaped RNA virus. The 2 strains found in the USA are Indiana-1 and New Jersey. Horses, donkeys, mules, cattle, swine, South American camelids and humans are affected. VSV is thought to be transmitted by insect vectors (sandflies and blackflies). Once introduced to a herd, VSV can be transmitted via direct contact through vesicular fluid or saliva. The incubation period is 2-8 days. Excessive salivation is often the first sign, followed by vesicles (blisters) on the lips, nostrils, hooves, teats and in the mouth. Most animals recover in 2 weeks. Laboratory tests rely on viral isolation or the detection of viral antigens. If suspected, the proper authorities are notified prior to collecting or submitting samples for diagnostic testing. During an outbreak, animal movement from the premise of interest is restricted and quarantine is started. Stabling is preferred if possible. No movement of animals for a period of 21 days after all lesions have healed is required. Insect control may help prevent disease spread. West Nile Encephalitis West Nile encephalitis is an arthropod-borne disease caused by West Nile virus (WNV). WNV is a mosquito-borne arbovirus in the genus Flavivirus, family Flaviviridae. WNV primarily infects birds, but is also found in horses, bats, cats, chipmunks, squirrels, domestic rabbits and humans. WNV was first observed in the US in NY in 1999 and has swept across the lower 48 states. Transmission is by the bite of an infected mosquito, primarily Culex species. The incubation period is 3-12 days. Most animal species infected with WNV are asymptomatic; occasionally horses show signs of encephalitis (lethargy, weakness, ataxia, muscle fasciculations, partial paralysis or death). Diagnosis requires isolation and identification of the virus or specific antibody testing. Direct transmission does not occur and quarantine is not necessary. Mosquito control and prevention of exposure reduces the risk of disease. In humans, WNV ranges from mild fever to meningoencephalitis to death. The case fatality rate is 3-15%. A vaccine is available for horses; no vaccine is currently available for humans. http://www.cdc.gov/ncidod/dvbid/westnile/ Yersiniosis Yersiniosis is caused by the bacterium Yersinia enterocolitica, a rod shaped bacterium. Yersiniosis is most commonly passed in the feces of sick pigs, or contracted via the consumption of poorly cooked pork or in contaminated milk. http://www.cdc.gov/healthypets/diseases/yersinia.htm Exotic/Foreign Animal Diseases of Concern thaty may or may not affect humans:
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