33. Epidemiology and prevention of zoonotic helminth and bacterial infections

Zoonoses

A disease that is naturally transmissible from vertebrate animals to humans and vice versa
> 60% of all infectious disease are zoonoses
Bacterial
- Listeria monocytogenes
- Brucella
- Leptospirosis
- Bacillus anthracis
- Tularaemia
- Q fever
- Salmonella
- Plague
- Shigella
Helminth
- Trichinella spiralsis
- Taenia solium
- Echinococcus

Listeriosis

Listeria monocytogenes
Reservoir
- Animals are often asymptomatic but have the bacteria in their feces
Transmission
- Faecal-oral
- Also found in processed meat, soft cheese
Can cause abortion in pregnant women
Prevention
- Pasteurizing dairy products
- Pregnant women should avoid soft cheeses and pre-packed salads
- Hand-washing

Brucellosis

Caused by brucella spp.
Epidemiology
- Occurs worldwide
- Most common in Mediterranean region
Reservoir
- Cattle
- Dogs
- Sheep
- Goats
- Pigs
Transmission
- Direct or indirect contact with animals
- Contaminated animal products
Symptoms
- Fever
- Arthritis
- Can infect any organ
  - Heart
  - Brain
Prevention
- Vaccination of animals
- Pasteurization

Leptospirosis

Leptospira spp
Epidemiology
- Most common in tropical areas
Reservoirs
- Many wild animals (rat, mouse)
Transmission
- Direct contact with urine of infected animals
- Indirect contact with urine
Clinical features
- Mild disease (fever, myalgia)
- Severe disease
  - Rare
  - High mortality
  - Haemorrhages
  - Acute kidney injury
Prevention
- Controlling rodent populations
- Avoid contaminated areas
- Improve water and food storage conditions

Anthrax

Bacillus anthracis
Epidemiology
- Very rare in western countries (0 – 2 cases per year)
Reservoir:
- Grass-eating animals (sheep)
Transmission
- By exposure to spores
- Eating contaminated meat
- Through skin
- Inhalation of spore
Clinical features
- Skin anthrax
  - Most common (95%)
  - If spore enters through skin
  - Necrotic skin eschars
- Lung anthrax
  - Very rare
  - If spore is inhaled
  - Haemorrhagic mediastinitis
  - 75% mortality
- Gastrointestinal anthrax
Prevention
- Vaccination of animals
- Protective equipment in workers

Tularaemia

Francisella tularensis
Reservoir
- Rabbits
- Hare
- Squirrels
Transmission
- Bite of infected insects (ticks, mosquitoes, flies)
- Contact with infected animal
- Eating undercooked infected meat
Symptoms
- Fever
- Lymphadenopathy

Q fever