Parasite Control: The Resistance Problem
A goat flock shows poor weight gain after being moved from browse-dominant vegetation onto continuously grazed short pasture. Which feeding behavior makes goats especially vulnerable to gastrointestinal nematodes?
Grazing
A hatchery reports chicks that die in the shell, followed by white diarrhea, pasted vents and early brooder mortality. Which disease fits best?
Pullorum disease
A poultry flock develops progressively spreading crusted lesions on combs and wattles. Histopathology reveals large eosinophilic intracytoplasmic inclusion bodies. What are these inclusions?
Bollinger bodies
A cattle operation investigates repeated abortions and weak calves. The veterinarian identifies a protozoal parasite whose definitive hosts include dogs, coyotes and wolves. Which organism is involved?
Neospora caninum
A welfare audit assesses nutrition, housing, health, behavioral interactions and the animal's resulting emotional experiences. Which structured assessment framework is being used?
The Five Domains Model
A flock has variable parasite egg counts, and the veterinarian wants to identify which animals contribute disproportionately to pasture contamination. What quantitative test should be performed?
Fecal egg count (FEC)
An avian respiratory outbreak responds poorly to penicillin. PCR identifies a bacterium capable of vertical transmission that lacks a cell wall. Which bacterial genus is implicated?
Mycoplasma
Following live fowlpox vaccination, a farm manager checks the wing-web vaccination sites seven days later. What finding indicates successful vaccine administration?
A vaccine take
An aborted bovine fetus is submitted for suspected neosporosis. Which fetal organs should be prioritized for histopathology and molecular testing?
Brain, heart and liver
A cattle handler repeatedly separates individual cows from their herd, causing hesitation, vocalization and resistance. Which natural behavioral instinct explains the response?
Herd instinct
After deworming, a flock's mean fecal egg count decreases from 1,000 to 180 eggs per gram. Based on the effectiveness threshold, what problem should be suspected?
Anthelmintic resistance
A layer flock develops rapid-onset facial swelling, nasal discharge, and reduced egg production. Several recovered birds continue to spread infection. Which organism is most likely?
Avibacterium paragallinarum
Several young chickens develop paralysis, weight loss and irregular gray pupils. Necropsy reveals enlarged peripheral nerves and visceral lymphoid tumors. Which disease best explains the findings?
Marek's disease
A bull appears reproductively healthy but is implicated in repeated breeding failure across several cows. A sexually transmitted protozoan is suspected. Which anatomical location is most appropriate for collecting a diagnostic sample from the bull?
Preputial and penile epithelial folds
A gilt operation introduces mature boars near replacement females to stimulate reproductive activity. Which reproductive management principle is being applied?
The boar effect
A farmer deworms every animal and immediately moves them onto a pasture with almost no existing parasite larvae. What population-level mechanism increases the risk of resistance?
Loss of refugia
A broiler flock has respiratory distress and increased mortality. Necropsy reveals fibrin covering the pericardium and liver capsule. Which organism most strongly fits the characteristic lesion combination?
Avian pathogenic Escherichia coli (APEC)
A Newcastle disease virus isolate kills inoculated chicken embryos in under 60 hours. What virulence category does it belong to?
Velogenic
A cattle herd has repeated early embryonic losses linked to venereal trichomoniasis. The cows may clear infection after several cycles, but the outbreak persists. Which group of animals is most important to identify and remove to interrupt transmission?
Infected carrier bulls
A stabled horse repeatedly grasps a fence with its incisors, arches its neck and makes a grunting sound. Which stereotypic behavior is most consistent with these findings?
Cribbing (crib-biting)
A veterinarian uses conjunctival color scoring to select sheep for deworming. A thin ewe scores 3, but a healthy adult scores 2. Which parasite is this system mainly designed to assess?
Haemonchus contortus
A turkey flock develops chronic respiratory disease with sinusitis. Testing implicates an organism that can spread through infected eggs, persist in carriers, and remain in the flock after antimicrobial treatment. What is the primary reason treatment alone may fail to eradicate it?
Persistent carrier infection
A chicken farm develops sudden, high mortality with hemorrhagic combs and wattles. Nearby migratory waterfowl appear clinically healthy. Which disease must be urgently investigated and reported to the appropriate authorities?
Highly pathogenic avian influenza (HPAI)
A sheep farm experiences abortions after introducing barn cats. Placental cotyledons contain necrotic lesions, and surviving lambs develop neurologic abnormalities. What infective environmental stage is responsible for transmission from the definitive host?
Sporulated Toxoplasma gondii oocysts
A group-housed pig operation records repeated tail biting despite adequate feed and absence of infectious disease. Which category of unmet welfare needs should be investigated most directly?
Behavioral and environmental needs