Cattle Health in Australia

The cornerstone of the Australian cattle health program is annual vaccination against clostridial diseases — the group of rapidly fatal bacterial diseases caused by Clostridium species that are ubiquitous in Australian soils. Blackleg, malignant oedema, pulpy kidney (enterotoxaemia), black disease, and tetanus can each kill a healthy, thriving animal within 24 to 48 hours of infection onset, with no prior warning signs. They are entirely preventable by vaccination, and the cost of vaccination ($3 to $6 per animal per year) is trivially small compared to the value of a single lost beast.

The standard protocol uses a 5-in-1 vaccine (covering the five main clostridial diseases) or a 7-in-1 (adding leptospirosis to the five clostridials). Leptospirosis vaccination is strongly recommended in herds where people — particularly children, pregnant women, or immunocompromised individuals — have regular close contact with cattle, as Leptospira species are readily transmitted to humans through contact with cattle urine or contaminated water.

The sensitisation protocol for naive (never-vaccinated) cattle requires two injections 4 to 6 weeks apart to establish protective immunity. After sensitisation, annual boosters maintain protection. Calves should receive their first clostridial vaccination at marking (4 to 8 weeks of age) with a booster at weaning; cows should receive their annual booster 4 to 6 weeks before calving, which also elevates the colostral antibody concentration that provides passive protection to newborn calves through their first weeks of life before they can be vaccinated directly.

Adult cattle develop significant acquired immunity to most gastrointestinal roundworms through repeated exposure — this immunological advantage over sheep and goats means that internal parasite management in adult cattle is less intensive and less economically consequential than in small ruminants. However, young cattle under 18 months have not yet developed this acquired immunity and are the primary target of a strategic cattle drenching program.

The key drenching events for cattle in Australia are: weaning (when nutritional stress and the loss of the partial protection provided by close proximity to the immune dam create peak susceptibility), and late summer or early autumn in high-worm-burden areas (coastal eastern Australia, high-rainfall tablelands) to reduce the worm population carried through winter. Faecal egg count monitoring from weaners in autumn identifies herds where worm burden is approaching production-impacting levels and guides treatment decisions.

Liver fluke requires specific attention in areas where the intermediate host snail (Lymnaea tomentosa) is present — primarily flooded river flats, irrigation areas, and permanently wet ground in southeastern Australia. Standard cattle drenches (macrocyclic lactones, benzimidazoles, levamisole) are not effective against liver fluke. Triclabendazole treats all lifecycle stages of fluke; closantel is effective against adult fluke only. If your property has wet areas with known snail habitat and cattle show poor condition, bottle jaw, or anaemia, test for fluke with a faecal egg count or blood GLDH test before treating.

The cattle tick (Rhipicephalus australis) is restricted to the tick-endemic zone of coastal and sub-coastal Queensland, small areas of northern NSW, and parts of the NT. Ticks transmit tick fever — babesiosis (caused by Babesia bigemina and Babesia bovis) and anaplasmosis (caused by Anaplasma marginale) — which cause severe haemolytic anaemia and can kill naive cattle rapidly.

The critical management principle for tick management is naive cattle introduction. Cattle from southern, tick-free Australia (Angus, Hereford, other British breeds) introduced to tick country without prior vaccination or gradual exposure can rapidly succumb to tick fever — the same animals that perform well in Queensland in tick-free conditions may die of tick fever within weeks of entering tick-endemic areas. Any cattle movement from tick-free to tick country requires vaccination (live tick fever vaccine available through state authorities) and careful management of the initial exposure period.

Brahman and Brahman-cross cattle that have been raised in tick country develop significant acquired resistance to tick infestation — their denser, oilier skin physically resists tick attachment, and their acquired immune response reduces tick reproductive success substantially. This tick resistance is one of the most important practical advantages of Brahman genetics in northern Australian beef production.

Bovine respiratory disease (BRD) is a disease complex involving multiple viral (IBR, BVD, PI3, bovine respiratory syncytial virus) and bacterial (Mannheimia haemolytica, Pasteurella multocida) pathogens that combines with stress (weaning, transport, mixing of mobs) to cause pneumonia. It is the most economically significant disease in feedlot cattle and important at weaning in all production systems. Signs include fever, nasal and ocular discharge, laboured breathing, and rapid weight loss. Early antibiotic treatment (within 24 hours of first signs) is critical — delayed treatment results in permanent lung scarring and chronically reduced performance. Vaccination against the viral component (IBR, BVD) reduces incidence.

Bovine viral diarrhoea (BVD) causes reproductive losses (early embryonic death, mummified foetuses, stillbirths, congenital defects), immunosuppression, and occasionally acute disease. The most significant BVD management challenge is the persistently infected (PI) animal — cattle infected in utero before immune system development that shed virus continuously throughout their lives. Identifying PI animals by ear notch ELISA testing and removing them from the herd is the most effective BVD control measure. Vaccination reduces disease severity but does not eliminate PI risk from purchased animals.

Bloat on lush legume pasture (clover, lucerne, medic) is frothy bloat — gas trapped in stable rumen foam cannot be eructated normally. Signs progress from slight discomfort to severe left-flank distension and death within a few hours. Prevention: dose cattle with poloxalene (a bloat prevention agent) in water or supplement before and during the risk period; allow cattle to fill on dry pasture before moving to lush legumes; introduce lush legume grazing gradually. Treatment of an acute case: tube the rumen with a stomach tube, administer vegetable oil or poloxalene, walk the animal.

Grass tetany (hypomagnesaemia) occurs in cows grazing lush, rapidly growing pasture — particularly on recently fertilised improved pastures in spring or after autumn rain — that is high in potassium and nitrogen but low in available magnesium. Signs: sudden onset of muscle tremors, ataxia, hypersensitivity to noise and movement, aggressive behaviour, and recumbency with convulsions. It is rapidly fatal without treatment — intravenous magnesium (subcutaneous 25% magnesium sulphate solution in 4 sites is the first-aid approach while waiting for a vet) and prevention through magnesium supplementation (magnesium oxide in lick or dusted on pasture) in at-risk periods.