Ten human diseases transmitted by animals

Zoonoses are diseases transmitted by animals. They appear during sudden epidemics, like SARS or avian flu, or are endemic, like plague or tularemia. What animals are reservoirs of zoonosis, how do we catch them, and what are their symptoms? Zoom on 10 zoonoses that still lurk.

Animals may be our friends, they are also vectors of diseases, called zoonoses. It is estimated that 60% of infectious diseases and 75% of emerging diseases described in humans are of animal origin. Sometimes harmless to their host, thepathogen can be fatal in humans.

SARS (Severe Acute Respiratory Syndrome)

  • Agent: Sars-CoV coronavirus.

  • Mode of contamination : droplets of saliva of infected people, contact with contaminated objects.

  • Animal tank: bat. Intermediate host: civet.

  • Symptoms: fever, chills, cough, difficulty breathing, shortness of breath, general malaise. The overall fatality rate is 15%, and up to 50% in people over 65 years of age.

  • Epidemiology: 8,300 cases identified between November 2002 and May 2003, mainly in China. 7 probable cases in France including one death.

Leptospirosis

  • Agent: bacterium ((Leptospira interrogans).

  • Animal tank: rodents, horses, cattle, pigs, dogs.

  • mode of contamination: by injured skin and mucous membranes, via contaminated urine.

  • Symptoms: fever, chills, headache, pains muscle and joint, which may progress to a hemorrhagic syndrome, renal, hepatic meningeal or pulmonary involvement. The leptospirosis is fatal in 5 to 20% of cases.

  • Epidemiology: 600 people each year in France, one million worldwide for severe forms.

Ebola

  • Agent: Ebolavirus (Zaire, Bundibugyo, Sudan, Reston, Taï Forest and Bombali).

  • Mode of contamination: direct contact with blood and with liquids life of infected people.

  • Reservoir animal: bat. Intermediate host: monkey.

  • Symptoms: sudden onset of high fever, intense weakness, muscle pain, headache, throat irritation. Subsequently, vomiting, diarrhea, rashes and in some cases internal and external hemorrhages. The mortality rate ranges from 25% to 90%.

  • Epidemiology: several epidemics restricted in the Democratic Republic of Congo (DRC), Uganda and Congo (1,590 dead between 1995 and 2007). The main outbreak occurred in West Africa between 2014 and 2016 (28,000 cases including more than 11,000 deaths). Since 2019, we observe a new resurgence in the DRC.

Lassa fever

  • Agent: arenavirus.

  • Mode of contamination: contact with animal urine or excrement.

  • Reservoir animal: rodent (Mastomys natalensis).

  • Symptoms: in 80% of cases, Lassa fever is asymptomatic. The most frequent clinical signs: fever, vomiting, nausea, abdominal pain, headache, muscle pain, intense fatigue. In severe forms: hemorrhages, edema, pericardial and pleural effusions. The mortality rate is 1%.

  • Epidemiology: Lassa fever is endemic in several countries in West Africa, where it infects 100,000 to 300,000 people a year.

Plague

  • Agent: bacteria (Yersinia pestis).

  • Mode of contamination: inhalation respiratory droplets from infected people, contact with infected body fluids, flea bites.

  • Animal tank: small mammals (transmission also by chip).

  • Symptoms: there are 2 main clinical forms: bubonic plague and the pulmonary plague. The plague bubonic results in a high fever and a bubo lymphatic around the bite that can progress to a sepsis deadly. The fatality rate ranges from 30% to 60% for the bubonic form and almost 100% in the pulmonary form in the absence of treatment.

  • Epidemiology: 3.248 cases of plague worldwide between 2010 and 2015, including 584 fatalities. The homes the most important are the Democratic Republic of the Congo, Uganda and especially Madagascar (between 250 and 500 cases per year). In France, the last case dates from 1945 (Corsica).

Avian Flu

  • Agent: virus type A (mainly H5N1 and H7N9).

  • Mode of contamination: direct contact with infected poultry, very rare cases of human-to-human transmission.

  • Reservoir animal: wild or domestic birds.

  • Symptoms: influenza-like illness (fever, headache, cough, etc.), then breathing difficulties which may progress to pneumonia and acute respiratory distress syndrome and septic shock.

  • Epidemiology: 562 cases between 2003 and 2011 for the H5N1 virus, including 329 fatal, mainly in China, Indonesia and Vietnam. Since 2013, 1,500 cases of H7N9 flu have been identified in China.

Rage

  • Agent: rhabdovirus.

  • Mode of contamination: bite or scratching of the contaminated animal, or licking on injured skin.

  • Reservoir animal: wild animals (bat, fox) and dog.

  • Symptoms: after a long asymptomatic phase (several days to several months), the patient develops dysphagia, paraesthesia and neuropsychiatric disorders (anxiety, agitation, hydrophobic). Death occurs within a few days due to cardiorespiratory arrest. The paralytic form (30% of cases) has a longer course, with progressive paralysis of the muscles from the place of the bite. The rage is fatal in almost 100% of cases.

  • Epidemiology: 59,000 annual deaths worldwide, mainly in Asia and Africa. 29 million people are vaccinated after being bitten.

Tularemia (hare fever)

  • Agent: bacteria (Francisella tularensis).

  • Mode of contamination: direct contact with infected animals or by tick bite, inhalation by air, consumption of contaminated meat or water.

  • Reservoir animal: wild mammals, mainly rodents (vole, field mouse …). Intermediate hosts: rabbit, hare, roe deer.

  • Symptoms: the most common form is ulceroglandular tularemia, with an ulceration at the point of entry of the bacteria, surrounded by erythema with sometimes suppuration. There are also forms ocular, thyphoid, pharyngeal or pulmonary depending on the route of contamination. Mortality rates vary from 5% to 30% for the pulmonary and typhoid forms.

  • Epidemiology: mainly, the wooded areas of thenorthern hemisphere (especially Canada and the United States), where the most severe forms are found. In Europe, the Scandinavian countries and the Balkans are the most affected. In France, there are around 30 to 130 cases per year.

Cat scratch disease

  • Agent: bacteria (Bartonella henselae).

  • Mode of contamination: scratching, biting or licking of bonded skin, transmission by chip.

  • Tank animal: cat.

  • Symptoms: inflammatory papule or pustule, accompanied by a condition febrile (myalgia, anorexia, asthenia). The healing is spontaneous in 90% of cases. In 5 to 10% of cases, the cat scratch disease gives rise to complications (suppuration, arthritis, neurological, ophthalmic or pulmonary involvement).

  • Epidemiology: 6.6 cases per 100,000 inhabitants.

Brucellosis

  • Agent: bacteria Brucella, mainly B. melitensis, B. arbotus and B. am.

  • Mode of contamination: direct contact or by secretions and excrement from sick animals, ingestion undercooked meat, raw milk or cheese, or by inhalation of dust.

  • Reservoir animal: cattle, sheep and goats and wild animals (Boar, deer, bison, caribou, Hare…).

  • Symptoms: chills, fever, headache severe, joint pain, general malaise. The brucellosis is fatal in less than 5% of cases, when the infection affects the brain, the meninges or the heart valves.

  • Epidemiology:brucellosis is rare in North America and Europe, but more common in the Middle East (around 100 cases per 100,000 people per year), around the Mediterranean, in Mexico and in Central and South America (farming areas) .

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