Joanna Grigg
Animals in poorly ventilated enclosed areas that are under fed, unused to captivity and stressed, are more likely to develop respiratory diseases than in their natural habitat.
It’s no surprise to Professor Cord Heuer, Massey University, that new variants of viruses develop in these situations, with a chance of exchange to humans close by. An example is Covid-19.
Heuer spends much of his research time on zoonotic diseases: diseases that transfer across animal and human or have the potential to do so.
He describes New Zealand’s traditional food production approach as the best system to limit the emergence or spread of zoonotic diseases.
“That’s because it’s based on grazing domesticised animals outdoors with good feeding, and generally low stress.”
“Our farmers and meat processors are more aware than farmers in many other countries as to the importance of protection and cleanliness during animal handling in milking sheds, woolsheds, yards and during tailing time and slaughter.”
Back in January the World Health Organisation reported Covid-19 likely originated from an animal source from a live animal market in China. Several known coronaviruses are circulating in animals that have not yet infected humans. As surveillance improves around the world, more coronaviruses are likely to be identified.
Heuer says viral zoonotic diseases are rare in NZ. Only two harmless parapox-virus diseases are known to be transmitted from ruminants to people in NZ (pseudocowpox or ‘milkers nodule’, contagious ecthyma or ‘scabby mouth’ of sheep).
“Some other potential zoonotic viruses are known to exist in birds but, typical for NZ, they have not infected people as yet.”
Rabies, avian flu, MERS or SARS cases have not been recorded. Swine flu may be an example but no pigs in NZ were known to be infected at the time, he said.
“Viruses are usually seen originating from wildlife animals living in captivity or in a market environment, or from bats in an area frequented by humans.”
Farmer vigilance is useful for observing diseases.
“Viral disease from birds are always a possibility as they travel a long way, but most of our birds come from Australia or are also colonising Australia on the way from Asia, and then come here.”
Bats are known to carry large ranges of bacteria and viruses including Ebola and rabies. Avian influenza was spread to humans from live chickens at markets in China, and then other Asian countries. Seafood kept live in markets can be another source, he said.
“It’s no surprise that it comes up in these situations.”
“It’s fostered by the environmental conditions so we need to be mindful of modifying the environment at times, for example indoor lambing or indoor wintering.”
One of the most serious zoonotic diseases to affect farmers in NZ is leptospirosis (bacteria transferred mainly through urine splash and air droplets contacting the mouth, nose or open skin). Flu-like and severe fatigue symptoms result and, if untreated, can lead to renal failure, muscle inflammation, and even encephalitis and meningitis.
Other zoonotic microbes to be aware of are the orf virus (known as scabby mouth in sheep and goats), the Toxoplasma parasite (humans, sheep, cats), the fungus ringworm, and roundworm parasites that exchange between humans and cats.
Bacteria such as E. coli 157 can be spread via animal urine entering water systems. Campylobacteria exists in gut fill so attention to food safety during calf rearing and meat processing is the best preventative.
It is important to wash hands before eating, (if you’ve been in contact with animals), treat pets for parasites and wear protection gloves when disposing of dead animals and assisting animal births.
