TRANSMISSION
• Brucella spp. infect humans as incidental hosts, with a low infectious dose (estimated at 10-100 organisms) required for transmission. 4 • Human infection occurs through exposure or direct contact with tissues or blood from infected animals, including placental tissues or fluids. • Aerosol transmission is also possible, particularly in laboratory environments. • Faeces from dogs fed meat/offal from feral pigs may be a potential source of infection as ingested organisms may remain viable during transit through the gastrointestinal tract.
IN HUMANS
PREVALENCE AND RISK FACTORS • In Australia between 1991 and 2019 an average of 30 human B. suis cases were reported annually, with most cases occurring in Queensland (80%). 4 • Most reported cases are due to occupational or recreational exposure to feral pigs through hunting and pig hunting dogs. Based on conservative estimates, there are more than 156,000 adult pig hunting dogs in Australia, at an average of three adult dogs per hunter. 11 • The main patient risk groups for Brucella suis infection are: 4 - Feral pig hunters and their families – direct or indirect exposure to feral pigs or their tissue products via skin abrasions and mucous membranes through the slaughter process and exposure to infected dogs. - Veterinarians and veterinary staff – exposure to infected dogs, especially during reproductive or obstetric surgery. - Dog breeders – exposure to reproductive tissues and fluids from whelping bitches. - Microbiology/laboratory staff – aerosol transmission, individuals working in microbiological facilities who handle Brucella cultures. CLINICAL DISEASE • Brucella infection (brucellosis) may be asymptomatic or symptomatic. Disease in humans can be multi- system but most typically presents with non-specific flu-like symptoms (fever, fatigue, myalgias, arthralgia) which may be relapsing or protracted. 12 • Cardiovascular complications may include endocarditis, myocarditis, pericarditis and infected aortic aneurysms. 13 • Osteoarticular involvement, usually seen as sacroiliitis in younger patients or vertebral infection (spondylitis, discitis and osteomyelitis) in older patients, is the most frequent complication of brucellosis (40% of cases). 13 • Neurological involvement (neurobrucellosis) can occur at any
Chronic hepatic brucellosis - calcified granuloma (arrow) with surrounding abscess, perforation into psoas and psoas abscess
stage of the disease with meningitis the most frequent central nervous system complication reported, estimated to occur in 5% of clinical cases. 13 • Genitourinary involvement (orchitis and epididymitis), and granulomatous hepatitis can also occur. • Human mortality is low (case fatality rate of 1-2%) and often related to cardiovascular complications. 4 • Brucellae can infect human chorioamniotic tissue at any stage of pregnancy, leading to obstetric complications including foetal death and abortion. 14 • Recurrent infections and relapses may occur in up to 10% of patients. 4 Some cases can manifest decades after primary exposure. • There is no evidence that disease is more likely or more severe in the young or old. • If human Brucella infection is suspected, serology and blood cultures are recommended. As Brucella is a laboratory hazard, identification must be performed in laboratories with appropriate facilities, and thus diagnosis may be delayed in regional or remote areas serviced by smaller laboratories. MALDI-TOF and PCR may be used for microbial identification. • Human-to-human transmission thought to be rare with casual contact.
CONTENTS
Companion Animal Zoonoses Guidelines 22
Made with FlippingBook - professional solution for displaying marketing and sales documents online