Page 1567 - Small Animal Internal Medicine, 6th Edition

CHAPTER 99 Zoonoses 1539

healthy carriers with more than one drug (www.capcvet.org). based on sanitation and control of exposure to feces. Immu-
If a pet is healthy but persistently Giardia-positive, genotyp- nodeficient people should avoid young animals and animals
VetBooks.ir ing can be performed to determine whether the assemblage from crowded or unsanitary housing, particularly if clinical
signs of gastrointestinal tract disease occur.
is zoonotic (www.dlab.colostate.edu).
Giardia vaccines for dogs or cats are no longer commer-
cially available in the United States. Prevention of zoonotic
giardiasis includes boiling or filtering surface water for BITE, SCRATCH, OR EXUDATE
drinking and washing hands that have handled fecally con- EXPOSURE ZOONOSES
taminated material, even if gloves were worn. In dogs and
cats treated for giardiasis, infection can be documented BACTERIA
again several weeks later in approximately 75% of animals. It is estimated that, between 2005 and 2009, there were
Thus the primary goal for the treatment of giardiasis is elimi- approximately 300,000 nonfatal dog bite injuries per year
nation of diarrhea. Whether these cases are a treatment in the United States (Quirk, 2012). Most of the aerobic and
failure or a reinfection is unknown. anaerobic bacteria associated with bite or scratch wounds
cause only local infection in immunocompetent individu-
BACTERIA als. However, 28% to 80% of cat bites become infected, and
Campylobacter spp., Escherichia coli, Helicobacter spp. Sal- severe sequelae, including meningitis, endocarditis, septic
monella spp., and Yersinia enterocolitica can each infect dogs arthritis, osteoarthritis, and septic shock, can occur. The
and cats, and can cause disease in humans. When pets with majority of the aerobic and anaerobic bacteria associated
Clostridium difficile are identified, the animal was likely with dog or cat bite or scratch wounds lead only to local
infected by a human and usually is a subclinical carrier. infection in immunocompetent individuals. Immunodefi-
Transmission from animals to humans is by fecal-oral cient humans or those exposed to Pasteurella spp., Capno-
contact. Dogs can be subclinical carriers of Shigella spp., but cytophaga canimorsus (DF-2), or Capnocytophaga cynodegmi
humans are the natural hosts. Although Helicobacter pylori more consistently develop systemic clinical illness. Sple-
was isolated from a colony of cats, whether dogs and cats are nectomized humans are at increased risk for developing
a common source of Helicobacter infection in humans is bacteremia.
unclear. However, on the basis of epidemiologic studies, it is Dogs and cats are subclinical carriers of multiple bacteria
unlikely. In most studies on prevalence of enteric zoonoses, in the oral cavity. After a person is bitten or scratched, local
Salmonella spp. and Campylobacter spp. infections were cellulitis is noted initially, followed by evidence of deeper
uncommon in pet dogs and cats. The prevalence of Salmo- tissue infection. Bacteremia and the associated clinical signs
nella and Campylobacter infections is greater in young of fever, malaise, and weakness are common, and death can
animals housed in unsanitary or crowded environments. occur within hours after infection with Capnocytophaga spp.
Gastroenteritis can occur in dogs or cats after infec- in immunodeficient or splenectomized humans. Diagnosis
tion by Salmonella spp., Campylobacter spp., or E. coli; Y. is confirmed by culture. Treatment of carrier animals is not
enterocolitica is probably a commensal agent in animals but necessary. Treatment of clinically affected humans includes
causes fever, abdominal pain, polyarthritis, and bacteremia local wound management and parenteral antibiotic therapy.
in humans. Helicobacter infections cause gastritis, which is Penicillin derivatives are highly effective against most Pas-
commonly manifested as vomiting, belching, and pica. Sal- teurella infections; penicillins and cephalosporins are effec-
monella spp. infection in dogs and cats is often subclinical. tive against Capnocytophaga spp. in vitro.
Approximately 50% of clinically affected cats have gastroen- Normal dogs and cats, as well as those with clinical signs of
teritis; many present with signs of bacteremia that usually disease, can carry methicillin-resistant Staphylococcus aureus
include fever (Tauni et al., 2000). Salmonellosis of cats and (MRSA) and Staphylococcus pseudintermedius (MRSP) on
humans has been associated with songbirds (songbird fever). the skin. These agents can be spread among veterinary or
Abortion, stillbirth, and neonatal death can result from in human patients and doctors, so this is a significant problem
utero infection. Diagnosis of Salmonella spp., Campylo- in hospitals (Febler et al., 2018; Weese et al., 2006). A recent
bacter jejuni, E. coli, and Y. enterocolitica is based on culture study of nasal and perianal samples completed in an open
of feces (see Chapter 91). A single negative culture may admission shelter showed MRSA in 0.5% of cat samples,
not rule out infection. Although PCR assays are available, MRSA in 0.5% of dog samples, and MRSP in 3% of dog
culture is superior because antimicrobial susceptibility can samples (Gingrich et al., 2011). These prevalence rates are
be determined. generally lower than those from dogs or cats from veterinary
Antibiotic therapy can control clinical signs of disease hospitals. These animals are generally not a risk for immuno-
from infection by Salmonella spp. or Campylobacter spp. (see competent and otherwise healthy people, but care should be
Chapter 28) but should not be administered orally to pets taken to avoid contamination of open wounds if an infected
because of the risk for antibiotic resistance. Parenteral drugs animal is being cared for. It is wise for veterinary hospitals
should be administered if bacteremia is suspected. Strains of to have an MRSA and MRSP policy for staff members; if
Salmonella resistant to most antibiotics have been detected repeated infections occur in veterinary cases, a staff member
in several cats. Prevention of enteric bacterial zoonoses is could be a carrier, so testing may been necessary.