Zoonoses Flashcards
What are zoonoses?
- Infections that can pass between living animals and humans
Why are infections such as malaria and Schistosomiasis not zoonoses?
Because even though transmitted from animals, they depend on the human host for part of their life-cycle
- According to lecture, don’t really understand that one
- Maybe because they aren’t really infections when in the host animals? Only become infections in humans
What are zoonoses caused by?
- Viruses
- Bacteria
- Parasites
- Fungi
What are some examples of bacterial zoonoses?
Salmonella Campylobacter Shigella Anthrax Brucella E-coli (verotoxigenic)
What are some examples of viral zoonoses?
Rabies
Avian influenza
Crimean-Congo haemorrhagic fever (CCHF)
Ebola virus disease
What are some examples of parasitic and fungal zoonoses?
Parasites:
Cysticercosis
Echinococcosis
Toxoplasmosis
Fungi:
Dermatophytoses
Sporotrichosis
How is rabies transmitted? Incubation period? Pathophysiology?
- Transmitted from the bites of infected animals (97% dogs but lots of potential reservoirs)
- Incubation period ranges from 2 weeks to several months
- Infection travels to the brain via peripheral nerves and causes encephalitis
What are some symptoms of rabies infection?
Encephalitis symptoms:
- Malaise, headache & fever
- Progressing to mania, lethargy & coma
- Over production of saliva & tears
- Unable to swallow & ‘hydrophobia’
- Death most often by respiratory failure
Investigations to diagnose rabies infection? Treatment?
- PCR of saliva or CSF
Immediately after bite post exposure prophylaxis:
- human rabies immunoglobulin (HRIG) around and into wound
- +4 doses of rabies vaccine over 14 days
- Rabies is always lethal if untreated.
How is the brucellosis infection transmitted?
Through exposure to any of 3 variants of Brucella (gram negative coccobacilli. Exposure via:
- Milking infected animals
- During parturition of the animals
- Handling carcasses of infected animals
- Consumption of unpasteurized dairy products
How does the Brucellosis infection tend to present?
Either acute, subacute, chronic or subclinical presentation:
Acute: Fever, weakness, headaches, drenching sweats and splenomegaly
Subacute: Fever and joint pains
Chronic: Flu-like symptoms. Malaise, depression, arthritis, endocarditis, splenomegaly
How long do the different presentations of Brucellosis tend to last? Which is the most common form?
- Subclinical: most common form
- Acute: 1 - 3 weeks
- Subacute: over 1 month
- Chronic: Lasts for months / years
Treatment of Brucellosis?
- Long acting Doxycycline for 2-3 months + Rifampicin, or + intramuscular gentamycin for first week(s)
- Add Cotrimoxazole for 2 weeks in CNS disease
How is Leptospirosis spread? How widespread a disease is it? How does it infect humans?
Through exposure to Leptospira genus of bacteria (spirochaetes)
- Many different host animals, widespread disease
- 11% of dairy workers have positive serology, with no history of illness
- Penetrates abraded skin or mucous membranes and causes systemic illness
What are the 2 most common forms of Leptospirosis and how do they tend to progress?
- L. icterohaemorrhagica (rat bites): Flu like symptoms – then jaundice, and renal failure
- L. hardjo (cattle): Fever, meningism – no jaundice
What is the general presentation of Leptospirosis? What are some possible severe complications?
- Undifferented fever; myalgia, headaches & abdominal pain
Weil’s disease (Triad of jaundice, AKI, bleeding)
Pulmonary haemorrhage (PH)
Case fatality 5-40%, >50% in PH
How is Leptospirosis diagnosed?
ELISA serology (suboptimal)
PCR
Culture – take at least one week on special media
How is Leptospirosis treated?
Lack of evidence that antibiotics are particularly effective, but most effective early in disease
- Doxycycline for mild disease, IV penicillin for severe
Prompt dialysis
Mechanical ventilation
How is Lyme Borrelios transmitted? What are some of the possible manifestations of the disease?
Transmitted by tick, Ixodes ricinus
- Erythema Migrans (EM)
- ACRODERMATITIS CHRONICA ATROFICANS (ACA)
- LYMPHOCYTOMA
- NEUROBORRELIOSIS (NB)
How does Erythema Migrans (EM) tend to present? How common is it in Lyme Borreliosis?
EM: present in 80-90% of cases
Occurs 3-90 days after the bite
- Presents as an expanding rash on the skin, can have single or multiple lesions
How does Acrodermatitis chronica atroficans (ACA) tend to present? Who is it more common in?
- present in European Lyme Borrelios, more common in the elderly
- Appears as bluish-red discoloration – progresses over months to years to atrophic phase
- Occurs on extensor surfaces of distal extremities
- Peripheral neuropathy common
How does lymphocytoma as a result of Lyme Borreliosis tend to present?
Bluish solitary painless nodule
Occurs on earlobe or areola
How does neuroborreliosis (NB) tend to present? How common is it?
- Approx. 15% of patients develop NB
- Triad of facial nerve palsy, radicular pain (pain “radiated” along a dermatome) & lymphocytic meningitis
- Onset of symptoms 1-12 weeks after bite
How does Lyme Borreliosis contracted in the USA tend to differ?
Cardiac disorders more common (8 – 10%)
- Carditis (peri-myocarditis)
- Heart block
Arthritis more common
- Large joints, often knees
How is Lyme Borreliosis diagnosed?
EM: clinical diagnosis
ACA and Lymphocytoma: clinical & serology
NB: clinical + laboratory findings (symptoms + CSF analysis for high WBC + blood & CSF serology)
How is Lyme Borreliosis treated?
Oral Doxycycline or Amoxicillin, or IV Ceftriaxone
Most manifestations treat for 21 days (28 in arthritis or ACA)
