Food Animal Zoonoses

Comprehensive practice flashcards covering the epidemiology, clinical signs, diagnosis, management, and public health impact of major food animal zoonoses including BSE, Brucellosis, Bovine Tuberculosis, Leptospirosis, Q-Fever, Tularemia, Anthrax, Taeniasis, and Trichinellosis.

What two epidemiological cycles maintain the rabies virus?

The urban cycle and the sylvatic cycle.

What percentage of documented annual rabies cases in the United States do domesticated animals account for, and which species are most commonly affected?

They account for less than $10\%$ of all documented cases annually, with most occurring in cats, cattle, and dogs.

What is the biological definition and basic mechanism of a prion?

A prion is a proteinaceous infectious particle that is smaller than the smallest known virus and causes normal cellular proteins to convert into copies of the prion, initiating a cascade of misfolded proteins.

Why are abnormal prion proteins exceptionally resistant to standard decontamination procedures?

They are insoluble in all but the strongest solvents, highly resistant to digestion by proteases, extremely resistant to heat, normal sterilization processes, sunlight, and rendering, and elicit no detectable immune response.

What is the incubation period, morbidity rate, and mortality rate of Bovine Spongiform Encephalopathy (BSE) in affected cattle herds?

The incubation period is $2\text{ to }8\text{ years}$, morbidity in affected herds is $2\text{ to }3\%$, and mortality is $100\%$.

What genetic characteristic is shared by all human cases of variant Creutzfeldt-Jakob Disease (vCJD)?

All human cases have been homozygous for methionine at codon $129$ of $\text{PrP}^C$ (normal cell-surface glycoprotein).

What is considered the gold standard post-mortem diagnostic test for Bovine Spongiform Encephalopathy (BSE)?

Immunohistochemistry (IHC) on brain, medulla, spinal cord, or brain stem tissue.

How do the typical age of onset and primary etiology differ between classic Creutzfeldt-Jakob Disease (CJD) and variant Creutzfeldt-Jakob Disease (vCJD)?

Classic CJD has an average age of onset of $65\text{ years}$ and is not linked to BSE-contaminated food, whereas vCJD has a mean onset age of $26\text{ years}$ and is contracted by consuming BSE-contaminated cattle products.

What blood and plasma donation restriction was instituted to mitigate the transmission risk of variant Creutzfeldt-Jakob Disease (vCJD)?

Deferral of individuals who traveled to or resided in the United Kingdom for $3$ or more cumulative months between $1980$ and $1996$.

What are the common and regional historical names used for Brucellosis?

Bang's Disease, Undulant Fever, Malta Fever, Mediterranean Fever, Enzootic Abortion, Epizootic Abortion, and Contagious Abortion.

What clinical syndrome does Brucella abortus typically produce in horses?

Fistulous Withers or Poll Evil, which is an exudative inflammation of the supraspinous bursa filled with clear viscous fluid that can rupture.

What diagnostic procedure for bovine brucellosis is shown in this image?

The Brucella milk ring test (showing positive and negative results).

What are the key physiological characteristics and environmental susceptibilities of Mycobacterium species?

They are Gram-positive, acid-fast bacteria belonging to the Mycobacterium tuberculosis complex, require oxygen for growth, are very heat sensitive, can be killed by a $1:9$ household bleach-to-water solution, but remain viable for extended periods in cold weather.

Which warm-blooded species serve as recognized wildlife maintenance hosts for Mycobacterium bovis in New Zealand, the United Kingdom, Canada, and the United States?

Brush-tailed opossums (and possibly ferrets) in New Zealand, badgers in the United Kingdom and Ireland, bison and elk in Canada, and white-tailed deer in the United States.

What are the sequential steps and specific timeframes for the Caudal Fold Test (CFT) and Comparative Cervical Test (CCT) in bovine tuberculosis surveillance?

The CFT is checked $72\text{ hours}$ post-injection by an accredited veterinarian; if positive, the CCT must be administered by a specifically trained State or Federal veterinarian either within $10\text{ days}$ or after $60\text{ days}$.

What are the two clinical phases of human leptospirosis and their characteristic manifestations?

The first is the acute or septicemic phase ($\approx 1\text{ week}$), characterized by abrupt fever, chills, conjunctival suffusion, and severe myalgia of the calves, back, and thighs; the second is the immune phase ($\le 30\text{ days}$ or more), marked by circulating antibodies, urinary shedding, and potential liver or kidney failure.

What are the primary Leptospira serovars maintained by rats, cattle, dogs, and pigs?

Rats maintain icterohaemorrhagiae and ballum; cattle maintain hardjo, grippotyphosa, and pomona; dogs maintain canicola and bataviae; pigs maintain pomona, tarassovi, and bratislava.

What is an important clinical and immunological limitation of commercial animal leptospirosis vaccines?

Immunity is serovar-specific, and although vaccines prevent clinical disease, they do not completely prevent infection or shedding of the organism.

What is the causative agent, cellular classification, and geographic distribution of Q-Fever?

Coxiella burnetii, an obligate intracellular proteobacterium found worldwide except in New Zealand.

What bacterial concentration of Coxiella burnetii can be released during parturition in an infected animal?

$10^9\text{ bacteria}$ per gram of placenta.

What are the clinical forms and treatment durations of Q-Fever in humans?

Acute Q-Fever presents as self-limiting flu-like illness, hepatitis, or atypical pneumonia ($30\text{ to }50\%$); chronic Q-Fever ($1\text{ to }5\%$) primarily presents as endocarditis ($45\text{ to }65\%$ fatal if untreated) and requires $2\text{ to }3\text{ years}$ of doxycycline therapy.

What is the proper method for removing a feeding tick from the skin as illustrated in clinical guidelines?

Grasp the tick as close to the skin surface as possible using fine-tipped tweezers and pull straight upward with steady, even traction without twisting or jerking.

What is the infectious dose of Francisella tularensis via inhalation or inoculation compared to ingestion?

$10\text{ to }50\text{ organisms}$ for inoculation or inhalation, compared to $10^8\text{ organisms}$ for oral ingestion.

Which arthropod vectors transmit Francisella tularensis in the United States?

Ticks (Dermacentor andersoni, Dermacentor variabilis, and Amblyomma americanum) and deer flies (Chrysops discalis).

What environmental conditions trigger sporulation in Bacillus anthracis, and why is opening a suspect carcass contraindicated?

Sporulation requires low-nutrient conditions and exposure to oxygen; opening a carcass exposes vegetative cells to atmospheric oxygen, causing highly resistant spores to form and contaminate the soil for decades.

What climatic pattern is classically referred to as 'anthrax weather' in the United States?

A wet spring followed by a hot, dry period that damages vegetation on alkaline soils through a sequence of flooding and drought.

What are the preferred antimicrobial treatments for Bacillus anthracis infections?

Ciprofloxacin (or other fluoroquinolones) is the treatment of choice, with penicillin and doxycycline serving as primary alternative options.

How do Taenia solium and Taenia saginata differ regarding their intermediate hosts and potential for human cysticercosis?

Taenia saginata uses cattle as intermediate hosts and does not cause cysticercosis in humans; Taenia solium uses pigs as normal intermediate hosts, but humans can serve as both definitive and intermediate hosts, resulting in human cysticercosis.

What minimum internal cooking temperature is required throughout meat to destroy Taenia larvae?

At least $56^\circ\text{C}$.

Why is the life cycle of Trichinella spiralis classified as a direct life cycle?

It completes all stages of development (larval maturation, adult reproduction, and newborn larval encystment within nurse cells in skeletal muscle) inside a single individual host.

What is the primary method of transmission for Balantidium coli, and how is it treated?

Transmission occurs through ingestion of infective cysts via contaminated food or water; treatment consists of tetracycline or metronidazole in humans and tetracycline in animals.