pets as source of illness

Introduction

pets often are prime contributors to allergies but they can also sometimes cause other illnesses and pet ownership should be considered when diagnoses are not clear
fortunately in Australia, pets do not carry rabies and related lyssaviruses although bats can carry similar viruses but these are rarely kept as pets
immunocompromised people are at particular risk for serious systemic infections from their pets
- Pasteurella - see warning below
- Bartonella encephalitis, neuroretinitis, and osteomyelitis
- Toxoplasmosis neuroretinitis
- parasites

most mammalian pets (but especially cats) and bird pets can have Pasteurella bacteria (most often Pasteurella multocida) in their mouths which can cause skin infection after a bite or if the pet licks an open wound or broken skin¹⁾
rarely, Pasteurella may cause life threatening infections in high risk patients, even from kissing their pet²⁾
- patients with compromised immunity, liver failure, diabetes, malignant tumors, the elderly or very young are at risk of severe Pasteurella infections such as pneumonia, meningitis, endocarditis, myopericarditis, mycotic descending aorta pseudoaneurysm, necrotizing fasciitis, or bacterial peritonitis
- bacterial meningitis is caused by a penetrating bite, skull fracture or skull surgery, and blood-borne bacteremia or a spread of the infection from the surrounding area. It may also be caused by directly licking, sniffing, kissing, or touching the animal.
- peritonitis caused by P. multocida infection may occur in patients undergoing peritoneal dialysis
- upper airway pasteurellosis is exceptional and is secondary to oropharyngeal carriage or contamination of the patient’s airways by domestic or farm animals

cat bites
- these can cause major deep infections due to their long narrow teeth and the presence of Pasteurella bacteria and often need surgical debridement and intravenous antibiotics as well as tetanus coverage
- 70-90% of healthy cats carry Pasteurella bacteria (most often Pasteurella multocida) in their mouths which can cause skin infection after a cat bite or if a cat licks an open wound or broken skin
- 3–18% of all dog bites result in a wound infection, compared to 20–80% of cat bite infections
- compared to dog bites, their longer narrower teeth pose a higher risk of osteomyelitis, tenosynovitis, and septic arthritis, as well as septic arthritis of damaged joints and joint prostheses
cat scratches
- these can result in either:
  - cellulitis
  - prolonged subacute illness due to cat scratch disease
toxoplasmosis
- mainly an issue for pregnant woman, young children or the immunocompromised
cutaneous tinea infection
intestinal worms:
- parasites like roundworms (Toxocara cati) and hookworms can be transmitted via cat faeces, causing skin irritations or stomach pain
gastroenteritis
- Salmonella and Campylobacter live in pet faeces and can cause gastro
ticks in Australia
- can jump from pets to humans and cause local irritation or, in the case of the paralysis tick and young children, paralysis

dog bites
- these are much more common than cat bites and tend to cause a more traumatic injury which also is likely to needed surgical debridement, repair, intravenous antibiotics and tetanus cover
20-50% of dogs have Pasteurella bacteria (most often Pasteurella multocida) is often in their mouths which can cause skin infection after a dog bite or if a dog licks an open wound or broken skin
cutaneous tinea infection
gastroenteritis
- Salmonella and Campylobacter live in pet faeces and can cause gastro
intestinal parasites:
- giardiasis mainly from drinking contaminated water
- hookworm and roundworm
  - larvae from dog faeces in soil can penetrate human skin (hookworm) or cause tissue damage if ingested (roundworm)
- hydatid disease
  - tapeworm eggs from dogs that can form cysts in human organs
ticks in Australia
- can jump from pets to humans and cause local irritation (eg. brown dog ticks or bush ticks) or, in the case of the paralysis tick and young children, paralysis

bird fancier's lung
- allergic hypersensitivity pneumonitis usually associated most with pigeons, budgerigars, parrots, poultry (but may also come from certain small mammals kept as pets)
- affects up to 20% of bird fanciers
psittacosis
bird flu / H5N1 / HPAI may rarely cause human infection
Salmonella gastroenteritis from poultry eggs

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