Zoonoses, different infections transmitted by animals

What is a zoonosis?

A zoonosis is an animal disease that is transmitted to humans. Humans are often an accidental host, acquiring disease through close contact with an infected animal which may or may not be symptomatic.

Which are the risk factors?

Physicians should always ask about when taking a medical history and formulating a differential diagnosis. In both the United States and Europe, the most common types of pets include dogs, cats, fish, birds, small mammals, and reptiles.

Many of the risks posed by having a pet can be reduced with good hygiene after handling, careful selection of pets, and a. New pets may pose a greater health risk. Adult pets are generally safer than younger animals, as they are less likely to engage in playful activities that include scratching and biting. Children are at higher risk of infection because they are more likely to have close contact with pets.

How are they transmitted?

There are many different routes of transmission that can cause pet-related infections, including:

• Infectious saliva that contaminates by bite, abrasions of the skin or mucous membranes.
• Hand-to-mouth transfer of microorganisms, cysts, or oocysts (eggs) from the feces of an infected animal.
• Insect bites when these vectors are carried home by pets or when the bites transmit diseases from a pet, which act as a reservoir of disease, to humans.
• Body fluid spray (eg, respiratory secretions, placenta)
• Scratches
• Contamination of water or the environment with pathogens that contain animal urine.
• Contamination of an object that is later put in the mouth.

What are animal-borne infections?

Infections transmitted through saliva

• Rage: in developing countries, dogs account for 90 percent or more of rabies cases transmitted to humans. On the contrary, in developed countries wild animals are the main animal reservoirs and are transmitted through a bite or lick. in dogs, it can have several phases. Dogs are most often infected by the bite of another infected animal. Rabies is transmitted to humans through saliva contaminated by biting, scratching, or licking a rabid animal. Rabies should be considered in the differential diagnosis of patients who present progressive acute encephalitis.
• Pasteurella: it can be found in the oral cavity of dogs (P. canis and P. dagmatis). The infection rate from penetrating dog bites ranges from 2 to 10 percent. It is common in cat and dog bites. Pasteurella can cause soft tissue infections after animal bites or scratches, although they can also cause septic arthritis and osteomyelitis.
• Capnocytophaga: It is part of the normal oral flora of dogs and cats. C. canimorsus can cause fulminant sepsis and meningitis, particularly in immunosuppressed patients. Animal bite wound infections with C. cynodegmi are a less serious infection that is generally confined to the skin and soft tissues.
• Brucella: Canis in dogs appears to be worldwide in distribution, but human infections with B. canis are rare. In contrast, the Brucella species that are frequently associated with human brucellosis are B. melitensis, B. suis, and B. abortus. Humans can become infected when exposed to the bodily fluids of a B. canis-infected dog. Most cases occur on farms.

Fecally transmitted infections

• Common zoonotic pathogens that cause canine gastroenteritis include Salmonella, Campylobacter, Cryptosporidium. Numerous parasitic diseases can be transmitted from dogs to humans through feces, including toxocariasis, cutaneous larva migrans, giardia, and echinococcosis.
• The Salmonella infections transmitted to humans generally result in mild and self-limited gastroenteritis.
• Giardia lamblia It's one of the gastrointestinal parasites more common. Transmission of infectious Giardia cysts to humans can occur through three routes: through water, food, or the fecal-oral route. The greatest risk of transmission comes especially from dogs and cats.
• Toxocara canis (dog roundworm) causes visceral larva migrans and ocular larva migrans in humans. These roundworms live in the small intestine of the dog as an adult and the eggs are shed in the feces. Human infections are caused by ingestion of eggs from contaminated hands, soil, or fomites. They are generally mild to asymptomatic and are associated with persistent eosinophilia.
• Ancylostoma caninum and A. braziliense they are the etiological agents of cutaneous larva migrans. The eggs are shed in the feces of infected cats or dogs. Humans (and pets) become infected when their skin comes into contact with soil contaminated with the larvae. The second stage larvae can penetrate the intact skin of humans and the pads of dogs and cats.

Infections from insect bites

Dogs can carry which can subsequently bite a human host and transmit infectious diseases. In addition, an infected dog can act as a reservoir for diseases transmitted by other arthropod vectors, such as mosquitoes and sand flies, which in turn, after feeding on the dog, can transmit the disease to humans through their bite. They can transmit many diseases, including Borrelia burgdorferi (Lyme disease), Ehrlichia (ehrlichiosis), Babesia microti (babesiosis), Francisella tularensis (tularemia), and Rickettsia rickettsii (Rocky Mountain spotted fever).

• Coxiella burnetii, the etiological agent of Q fever is a worldwide zoonosis. The most commonly identified sources of human infection are farm animals, but dogs can also rarely serve as a source. Infected mammals shed C. burnetii in contaminated urine, feces, milk, and animal birth products. In humans, exposure results from inhalation of contaminated aerosols. The clinical signs of Q fever are often extremely mild or absent. Patients may be asymptomatic or may present acutely with one of three clinical presentations: a self-limited flu-like illness; Pneumonia; Hepatitis. Chronic infection most commonly affects the heart as endocarditis.
• Leptospirosis: Leptospira interrogans, the etiologic agent of human leptospirosis, infects a variety of both wild and domestic mammals, including dogs. Transmission to humans occurs by contact with contaminated water or soil with urine from infected animals (predominantly rats). Leptospirosis usually presents with the abrupt onset of fever, chills, myalgia, and headache, after an incubation period of 2 to 26 days (average 10 days). Many patients have an associated non-productive cough, nausea, vomiting, and diarrhea.

How can they be prevented?

It is important that animals are examined by a veterinarian on a regular basis, treated immediately for diarrhea and dermatosis and should be vaccinated against rabies. Animals confined indoors present a lower risk than those that roam outdoors. They should not eat raw meat or eggs. They should not be allowed to eat garbage, feces, or hunt. They should not be allowed to drink non-potable water (for example, surface water or toilet water).

To reduce the risk of owners scratching them.

Must be deworm animals frequently.

Owners should wash their hands after contact and after contact with pet food.

Specialist in Family and Community Medicine