Biology • Year 12 • Module 7 • Lesson 7
Disease in Agriculture — Animals
Lock in the key pathogens, their pathogen types, and the distinction between direct and indirect economic effects of animal disease in Australia.
1. Term–definition match
The definitions below are shuffled. In the right-hand column write the matching term from this list: foot-and-mouth disease, notifiable disease, biosecurity, culling, indirect economic effects, export market access, bovine viral diarrhoea (BVD), hydatid disease, Mycobacterium bovis, persistently infected (PI) cattle. 10 marks
| # | Definition (shuffled) | Matching term |
|---|---|---|
| 1.1 | A highly contagious viral disease affecting all cloven-hoofed animals, including cattle, pigs, sheep and goats; Australia has been free since 1872. | |
| 1.2 | A disease that must be reported to government authorities because of its economic significance or risk to public health. | |
| 1.3 | Measures used to prevent animal diseases entering or spreading through farms and across national borders. | |
| 1.4 | The destruction of infected or at-risk animals to prevent disease spread — an emergency management tool. | |
| 1.5 | Costs that result from an animal disease but are not the direct loss of productive animals — including trade bans, movement restrictions, and loss of consumer confidence. | |
| 1.6 | The ability to sell agricultural products to overseas buyers who require disease-free certification from the exporting country. | |
| 1.7 | A viral cattle disease caused by Pestivirus that leads to reproductive failure and immunosuppression, costing Australian producers over $100 million annually. | |
| 1.8 | A parasitic disease of sheep and cattle caused by larvae of a tapeworm that form cysts in the liver and lungs; dogs are the definitive host. | |
| 1.9 | The bacterium responsible for bovine tuberculosis; a slow-growing respiratory pathogen that can infect both cattle and humans. | |
| 1.10 | Cattle infected with BVD virus before birth that shed the virus for life without showing clinical signs of illness. |
2. True or false — with correction
Circle T or F. If the statement is false, write the corrected version on the line below. 10 marks (1 for T/F, 1 for each correction)
2.1 Foot-and-mouth disease is caused by a bacterium and primarily affects cattle by damaging their respiratory system. T / F
2.2 The economic impact of an animal disease is limited to the market value of animals that die or are culled during an outbreak. T / F
2.3 Australia declared provisional freedom from bovine tuberculosis in 1997, maintaining market access to countries that require bTB-free status. T / F
2.4 Culling all infected and at-risk animals is always the most effective and cost-efficient response to any animal disease outbreak. T / F
2.5 Geographic isolation alone is sufficient to protect Australia from exotic animal diseases like foot-and-mouth disease. T / F
3. Function and effect recall
Answer each question in 1–2 sentences using precise lesson terms. 8 marks (2 each)
3.1 What is the function of the National Livestock Identification System (NLIS) in protecting Australia's disease-free status?
3.2 Why do importing countries impose trade bans on livestock products from a country where FMD is detected, even when most animals in that country are unaffected?
3.3 What is the role of farm dogs in the transmission of hydatid disease (Echinococcus granulosus) to sheep?
3.4 Why do veterinarians recommend routine deworming of farm dogs as the primary control strategy for hydatid disease, rather than treating sheep with anthelmintics?
4. Fill in the blanks — FMD and the cost of outbreak
Complete the paragraph using the word bank below. Each word is used once. 8 marks
Word bank: aerosol • Aphthovirus • biosecurity • cloven-hoofed • export • fomites • indirect • quarantine
Foot-and-mouth disease is caused by _______________________, a member of the Picornaviridae family. It infects all _______________________ animals, including cattle, pigs, sheep, goats and deer. The virus spreads via direct animal contact, short-range _______________________ (it can travel several kilometres in favourable winds), contaminated feed, vehicles and _______________________ such as clothing and footwear. When FMD is detected in a country, most major _______________________ markets impose an immediate ban on livestock products from that nation. These trade losses are classified as _______________________ economic effects because they extend far beyond the farm. In Australia, maintaining FMD-free status is estimated to be worth over $80 billion annually in _______________________ market access — explaining why border _______________________ is treated as a national priority.
5. Build a concept map — direct vs indirect effects
Draw labelled arrows between the six terms below to show how an FMD outbreak flows from pathogen entry to economic consequence. Each arrow must carry a linking phrase (e.g. “triggers”, “leads to”, “reduces”). Aim for at least 6 labelled arrows. 6 marks
Supplied terms: FMD outbreak • culling of livestock • export market ban • biosecurity response • direct economic loss • indirect economic loss
6. Classify the disease transmission routes
The diagram below shows five routes by which FMD virus can spread between farms. Label each route (A–E) from the options given, then for each route tick whether it is a “direct” or “indirect” transmission pathway. 10 marks (2 each)
Route options: aerosol drift • contaminated vehicle • direct animal contact • infected feed/water • person carrying fomites
| Route | Name of transmission route | Direct? | Indirect? |
|---|---|---|---|
| A | |||
| B | |||
| C | |||
| D | |||
| E |
Q1 — Term–definition matches
1.1 foot-and-mouth disease • 1.2 notifiable disease • 1.3 biosecurity • 1.4 culling • 1.5 indirect economic effects • 1.6 export market access • 1.7 bovine viral diarrhoea (BVD) • 1.8 hydatid disease • 1.9 Mycobacterium bovis • 1.10 persistently infected (PI) cattle.
Q2 — True / false with correction
2.1 False. Correction: FMD is caused by a virus (Aphthovirus, Picornaviridae), not a bacterium. It causes painful blisters on the mouth and feet of cloven-hoofed animals, not respiratory disease.
2.2 False. Correction: The economic impact extends well beyond the direct loss of animals. The largest impacts are often indirect effects: export market bans, movement restrictions, loss of consumer confidence, and government emergency response costs. In the 2001 UK outbreak, direct agricultural loss was ~£2.7 billion but total economic cost exceeded £8 billion.
2.3 True.
2.4 False. Correction: Culling is appropriate for some highly contagious diseases with no vaccine, but the optimal response depends on the disease type, availability of vaccines, and transmission characteristics. Vaccination (Newcastle disease), test-and-remove programs (bTB), and management of PI animals (BVD) are more appropriate for other diseases. Mass culling also carries significant economic and welfare costs.
2.5 False. Correction: Geographic isolation provides a passive barrier but is not sufficient alone. FMD and other pathogens can enter via contaminated food products carried by travellers, live animal imports, and airborne aerosol spread. Australia relies on active biosecurity measures — border inspection, import controls, surveillance — not geography alone.
Q3.1 — Function of NLIS (2 marks)
The National Livestock Identification System provides individual electronic identification for all cattle, sheep and goats in Australia. In a disease outbreak, it enables rapid tracing of animal movements so that all animals that may have been exposed can be identified and quarantined quickly, limiting spread and maintaining confidence in disease-free status for export markets.
Q3.2 — Why import bans affect the whole country (2 marks)
Importing countries require certified disease-free status from the entire exporting nation, not just disease-free farms. When FMD is detected anywhere in Australia, the country loses its disease-free certification. Importing countries cannot be confident that any animal product from Australia is free of contamination, so they ban all imports as a precaution until the country regains certified disease-free status.
Q3.3 — Role of dogs in hydatid transmission (2 marks)
Dogs are the definitive host for Echinococcus granulosus: adult tapeworms live in dog intestines and shed microscopic eggs in faeces onto pasture. Sheep (and cattle) acting as intermediate hosts ingest the eggs while grazing on contaminated pasture. Larvae hatch in the gut and migrate to the liver and lungs, forming fluid-filled cysts. These organs are condemned at slaughter, causing direct production loss.
Q3.4 — Why deworming dogs, not treating sheep (2 marks)
Sheep are intermediate hosts; they harbour larval cysts in their organs but do not shed eggs. Farm dogs are the definitive hosts that shed infective eggs onto pasture. Breaking the cycle at the dog stage (by regularly deworming dogs with anthelmintic drugs) prevents egg contamination of pasture in the first place. Treating sheep with anthelmintics targets adult worms, but sheep do not harbour the adult stage of this parasite, so sheep treatment would be ineffective against the transmission cycle.
Q4 — Cloze answers (in order of blanks)
Aphthovirus • cloven-hoofed • aerosol • fomites • export • indirect • export • biosecurity.
Note: “export” appears twice — once as “export markets” and once as “export market access”.
Q5 — Sample concept map
Correct arrows include:
- FMD outbreak —triggers→ culling of livestock
- FMD outbreak —triggers→ biosecurity response
- FMD outbreak —causes→ export market ban
- culling of livestock —contributes to→ direct economic loss
- export market ban —is the main source of→ indirect economic loss
- biosecurity response —costs contribute to→ indirect economic loss
- indirect economic loss —exceeds→ direct economic loss
Award full marks for at least 6 correctly labelled arrows with accurate causal direction and appropriate linking phrases.
Q6 — Transmission route classification
A = aerosol drift (indirect) • B = contaminated vehicle (indirect) • C = direct animal contact (direct) • D = infected feed/water (indirect) • E = person carrying fomites (indirect).
Only direct animal contact (C) is a direct transmission route. All other routes involve an intermediate medium, object or person.