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A zoonotic disease, also known as zoonosis, is when the disease is transmitted in natural conditions from vertebrate animals to humans. The etiological factors of zoonoses can be bacteria, viruses, parasites, fungi or prions. What zoonoses are there? Here are some examples.
Cat scratch disease
The disease is caused by bacteria of the genus Bartonella, mainly Bartonella henselae, causing unilateral lymphadenitis. Cats are a natural reservoir of bacteria and the disease develops as a result of direct contact with an infected cat, especially its saliva. It is believed that these bacteria can also spread through cat fleas.
Bacteria enter our body at the site of a scratch or bite by a cat. Symptoms of the disease appear after about 1 – 8 weeks.
The classic picture of the disease is acute, subacute or chronic inflammation of one or more lymph nodes in close proximity to scratches or bites. The diseased lymph nodes are enlarged, painful, hard at first, then soft, and the skin over them red. Very often they are instilled with spontaneous emptying of the purulent content or may require a surgical incision. In most cases, there are no symptoms other than enlarged lymph nodes. However, this disease can also be associated with fever, general malaise or pneumonia. The disease usually resolves spontaneously after 4-6 weeks, without late complications.
The disease is most often diagnosed based on the clinical picture and the fact that a cat bites or scratches it. Histopathological examinations of the collected nodes and serological examinations may also be helpful in the diagnosis.
The treatment uses antibiotics from the group of macrolides (azithromycin) or tetracyclines (doxycycline). Because it heals itself, most people with cat scratch disease do not require treatment. Antibiotic therapy is recommended mainly in people with decreased immunity and with severe inflammation of the lymph nodes.
brucellosis
Currently, this disease is an exotic disease for us, as no cases of brucellosis have been reported in cattle since 1980, and in pigs in Poland since 1994. As a result of extensive actions of the veterinary services, it was possible to eradicate brucellosis in our country.
Unfortunately, this disease is widespread all over the world and common, among others, in Turkey, Greece and other countries of Southern Europe. All cases recorded in recent years in our country are related to falling ill while traveling to the above-mentioned countries.
Brucellosis is caused by bacteria of the genus Brucela, and their reservoirs, depending on the species, are domestic animals such as cattle, sheep, goats, pigs and wild animals such as wild boars, roe deer, deer and elks. Bacteria are excreted in the animals’ milk, urine and faeces. A person becomes infected as a result of the penetration of bacteria through injured skin, conjunctiva or through consumption of contaminated raw milk or its products. People who contracted brucellosis most often contracted the infection while tasting cheese and other dairy products during trips to villages or tasting at food fairs.
The incubation period of the disease is on average 1-3 weeks. Bacteria cause a variety of organ and systemic changes. The disease can take the form of:
- acute – wavy fever (with increases and decreases), chills, coarse sweats, general weakness, joint and muscle pain, headache, testicular pain, skin rash, neurological and psychiatric disorders (meningitis, polyneuritis, multiradicular inflammation ), enlargement of the liver and spleen
- chronic – most often it is the descent of the acute form; may be characterized by back pain, joint pain or muscle pain; hearing impairment, testicular damage or menstrual disorders, general weakness, chronic headaches may occur
The diagnosis of the disease is based on serological diagnostics, and the acute treatment is reduced to antibiotic therapy and, in the later stages of the disease, to complex symptomatic treatment (ENT, neurological, sanatorium).
The disease is prevented by strictly isolating sick animals and not allowing unpasteurized milk and dairy products from unknown sources to be marketed.
Leptospirosis
Acute feverish illness caused by bacteria of the genus Leptospira. Rodents are a natural reservoir of bacteria, but also dogs and other pets. In animals, there is a period of asymptomatic carriage for many months, during which bacteria are excreted in the urine.
Man becomes infected through damaged skin, conjunctiva or mucosa (e.g. while swimming in contaminated water bodies).
The disease may be asymptomatic, either as a febrile disease or as a severe multi-organ damage syndrome (the so-called Weil’s disease). Most often it proceeds as a generalized fever disease with a spontaneous recovery. The incubation period of the disease is approximately 10 days. Initially, severe headaches and muscle aches develop with fever and chills, followed by conjunctival ecchymosis. After about a week, the fever decreases and symptoms of meningitis, optic neuritis and peripheral nerve inflammation appear. The disease goes away on its own.
Leptospirosis in the form of Weil’s disease has a worse prognosis with a higher mortality (up to 40%) – there is a multi-organ damage manifested by jaundice, renal failure, hemorrhagic diathesis and disturbed consciousness.
Leptospirosis is most often diagnosed on the basis of serological diagnostics.
Antibiotics are used in the treatment, first of all, therapy with penicillin or ampicillin is prescribed.
Ornithosis — papuzia disease
Zoonosis caused by Chlamydia psittaci bacteria in birds as their reservoirs. Chlamydia strains transmitted by parrots or turkeys are believed to be more virulent than those transmitted by other birds. Bird breeders, veterinarians and pet shop sellers most often suffer from the disease.
Infection occurs through inhalation of faeces or other excreta from infected birds.
The disease can take various forms: from asymptomatic to feverish with headaches, sore throat and general weakness to severe atypical pneumonia (fever, dry cough).
In rare cases, it may be meningitis or endocarditis.
The diagnosis of the disease is based on serological tests. Tetracyclines are used in the treatment.
Mirosław Jawień, MD, PhD
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