Zoonotic diseases

• Zoonoses are diseases of animal origin that can affect people, with more than half of all known infectious diseases in humans being zoonotic
• Zoonotic diseases can spread to humans through close contact with infected animals, contact with saliva, blood, urine, or feces of an infected animal, contaminated water or soil, being bitten by an infected tick or mosquito, and consuming unpasteurized dairy products, undercooked meat, or unwashed fruit and vegetables contaminated with feces from an infected animal
• Emerging diseases are new diseases that have appeared in a population for the first time or are rapidly increasing in incidence or geographic range, with 75% of emerging pathogens in humans being zoonotic diseases
• Causes of zoonosis include contamination of food or water supply, farming, ranching, animal husbandry, wildlife trade, animal attacks, and pets like dogs and cats that can transmit diseases such as rabies, toxoplasmosis, and cat-scratch disease
• Zoonotic transmission can occur through various methods like direct contact, through faeces, by air (aerosol), animal bites or saliva, and through insect "vectors" like mosquitoes, fleas, and ticks
• Viral zoonoses include diseases like rabies, monkeypox, avian flu, West Nile Virus, Eastern Equine Encephalitis, Hantavirus, and Lymphochoriomeningitis
• Rabies is endemic in the U.S. and most of the world, spread by the bite of an infected animal, with clinical signs including behavior changes, leg paralysis, drooling, and difficulty swallowing, and almost 100% infected die
• Monkeypox is transmitted through direct contact, carriers include rats, prairie dogs, and rabbits, with symptoms in people including fever and pox-like rash 1-2 weeks after handling rodents
• Lymphochoriomeningitis (LCMV) is mostly a problem in geriatric and immunocompromised people, carriers are rodents including pocket pets like hamsters, with symptoms ranging from flu-like symptoms to neurologic problems like rabies
• West Nile and Eastern Equine Encephalitis are transmitted through mosquito bites, with symptoms in horses being neurologic problems and in people, fever and signs of meningitis
• West Nile and Eastern Equine Encephalitis:

  • Carriers: horses, birds, and other animals
  • Transmission: mosquito bite
  • Symptoms in horses: neurologic problems
  • Symptoms in people: 90% do not become ill, but in the geriatric and immunocompromised, symptoms include fever, signs of meningitis (neck pain, headache, neurologic problems)
  • Treatment: supportive
  • Prognosis: fatal in a small number of people
  • Prevention: mosquito control, vaccinate horses
• Bacterial Zoonoses include diseases like Cat Scratch Fever, Kennel Cough, Lyme Disease, Undulant Fever, Parrot Fever, Tetanus, Tularemia, Leprosy, Tuberculosis, and more
• Cat Scratch Fever (Bartonella henselae):

  • Carriers: cats infected by a flea bite
  • Transmission: not directly from cat to cat, but from cat to person by bite or scratch
  • Symptoms in cats: many are asymptomatic carriers, may have fever and lethargy, enlarged lymph nodes
  • Symptoms in people: relapsing fever, enlarged lymph nodes, inflamed lymph vessels, liver and spleen infections, infected heart valves (endocarditis), mostly in immunocompromised people and children
  • Treatment: Azithromycin, Clarithromycin, Ciprofloxacin
  • Prognosis: good if treated
  • Prevention: control fleas and ticks, treat cats with antibiotics, test cats owned by immunocompromised people for Bartonella spp
• Lyme Disease:

  • Affects dogs and humans (not cats)
  • Caused by Borrelia burgdorferi transmitted by deer ticks (Ixodes spp.) that must be attached for at least 24 hours to cause infection
  • Symptoms: early stage includes skin rash at the tick bite, fever, muscle aches, enlarged lymph nodes; late stage includes neurologic, kidney, heart disease, and arthritis
  • Treatment: doxycycline, amoxicillin, cefuroxime
  • Prognosis: difficult to cure in dogs, treatable in people if treated early, difficult to cure chronic infections in people
  • Prevention: control ticks, non-core vaccine available for dogs
• Undulant Fever (Brucella canis):

  • Carriers: dogs (can be asymptomatic), cattle, pigs
  • Transmission: contact with urine, discharge of Oestrus (heat), afterbirth, aborted fetuses
  • Symptoms in dogs: inflamed testicles, scrotal dermatitis, enlarged lymph nodes or spleen, weight loss, poor hair coat, abortion, neonatal death, sick puppies, eye infections, infections in the disks in the back
  • Symptoms in people: fever, chills, sweats, malaise, headache, muscle aches, back ache, weight loss, enlarged lymph nodes or spleen
  • Treatment: doxycycline, vibramycin, streptomycin, tetracycline, rifampin
  • Prognosis: immunocompromised people and children more likely to get infected, tends to relapse and difficult to cure in dogs and people
  • Prevention: wear gloves, wash hands when handling female dogs in heat, aborted puppies, or urine
• Brucellosis (Brucella abortus):

  • Affects ruminants (cattle) and humans
  • Also known as contagious abortion
  • Transmission: eating contaminated food, including raw meat and unpasteurized milk of infected animals (cattle, sheep, goat, pigs)
  • Prevention: avoid unpasteurized dairy foods, cook meat thoroughly, wear gloves, take safety precautions in high-risk workplaces, vaccinate domestic animals
• Parrot Fever (Chlamydia psittaci):

  • Affects birds and can be transmitted to cats and people
  • Transmission: through faeces and nasal discharge from infected birds
  • Symptoms: upper respiratory, gastrointestinal, and hepatitis symptoms in carriers; flu-like and respiratory symptoms in people
  • Treatment: tetracycline, doxycycline
  • Prognosis: good with treatment
• Leptospirosis (Weil’s disease):

  • Caused by Leptospira interrogans
  • Carriers: warm-blooded wildlife, rodents, livestock, dogs
  • Transmission: through urine, direct contact with urine from infected animals, or through contaminated water, soil, or food
  • Symptoms: chronic urinary tract infection, kidney failure, liver failure (jaundice), fever
  • Treatment: treat liver and/or kidney failure, penicillins to treat the disease, tetracycline to eliminate the carrier state
  • Prognosis: 85% do well if treated
  • Prevention: dog vaccine for 4 serovars, handle dog urine with gloves, wash hands, protect mouth and eyes when hosing kennels
• Rat Bite Fever:

  • Caused by Streptobacillus moniliformis and Spirillum minus
  • Carriers: rodents, especially rats
  • Transmission: through urine, faeces, or mucous secretions, bite (slow healing, inflamed wound)
• Dog vaccine for 4 serovars provides immunity lasting about a year
• Preventive measures for handling dog urine: use gloves, wash hands; protect mouth and eyes when hosing kennels
• Rat Bite Fever is caused by Streptobacillus moniliformis and Spirillum minus, transmitted through urine, feces, or mucous secretions, with symptoms in people including recurring fever and gastrointestinal upset
• Treatment for Rat Bite Fever involves antibiotics like doxycycline, erythromycin, penicillin, and amoxicillin, with good prognosis if treated
• Rickettsial Zoonoses involve Rickettsia, small bacteria-like organisms carried by ticks or fleas, with Rocky Mountain Spotted fever caused by Rickettsia ricketsii
• Transmission of Rocky Mountain Spotted Fever occurs through ticks, with symptoms in dogs including fever, back pain, lethargy, swollen ears, nose, face, underbelly, kidney failure, and low platelet count
• Treatment for Rocky Mountain Spotted Fever includes antibiotics like doxycycline and cortisones, with a good prognosis if treated early
• Typhus, transmitted by flea or louse bite, presents flu-like symptoms, backache, fever, and a dull red rash, with excellent prognosis with antibiotics
• Fungal Zoonoses like Blastomyces, Coccidioides, Cryptococcus, Dermatophytes, Histoplasma, and Sporothrix have various manifestations and treatments
• Ringworm, a fungal infection of the skin, is more severe in cats than dogs, transmitted through direct contact or fomites, and can be challenging to eliminate from shelters
• Treatment for Ringworm varies from topical treatments like Tresaderm, Lotrimin, Lymdyp for mild cases to oral antifungals like griseofulvin, itraconazole, fluconazole, terbinafine for severe cases
• Protozoal Zoonoses include Coccidia spp., Cryptosporidium parvum, Giardia causing Beaver Fever, Toxoplasma gondii, and Encephalitozoon cuniculi
• Cryptosporidium, affecting warm-blooded animals, is transmitted through fecal-oral route, with treatment using anti-parasitic drug nitazoxanide and good hygiene for prevention
• Giardia affects dogs and cats, causing diarrhea and vomiting, with diagnosis through fecal wet mount or flotation, and treatment with metronidazole or fenbendazole
• Toxoplasmosis, carried by cats, is transmitted through contact with cat feces, with varying symptoms in cats and people, and treatment with antibiotics like pyrimethamine and sulfadiazine
• Prevention of Toxoplasmosis involves avoiding raw meat, unwashed vegetables, cleaning litter boxes daily with gloves, and pregnant women avoiding contact with cat feces
• Helminth Zoonoses include various worms like Ancylostoma caninum, Bayliascaris procyonis, Tapeworms, Echinococcus granulosa, Taenia spp., and Toxocara cati
• Arthropod Zoonoses involve bugs like ticks, fleas, and arachnids, with preventive measures including vaccinations, hand hygiene, wearing protective gear, and disinfecting wounds
• Reportable Zoonotic Diseases like Anthrax, Brucellosis, Eastern Equine Encephalitis, West Nile Virus, Hantavirus, and Lyme Disease must be reported to local/state health departments