What do we know about pinkeye in Central Australia?

Region: Central Australia | Topic: Livestock
Feb 2021

Watering down yards helps to reduce dust which can be an eye irritant. Damaged eyes are more susceptible to disease.

Above: Watering down yards helps to reduce dust which can be an eye irritant. Damaged eyes are more susceptible to disease.

The summer of early 2020 will be remembered as one of the worst ever for flies in Central Australia. For many stations it was also a particularly bad time for pinkeye in cattle. Pinkeye or infectious bovine kerato-conjunctivitis (IBK) is an inflammation of the eye that can lead to blindness in severe cases.

The prevalence of pinkeye on some properties prompted the Alice Springs Industry Advisory Committee (ASPIAC) to invite an interstate researcher to speak at the mid-year ASPIAC meeting. Dr Mac Kneipp, a vet based on the east coast currently doing his PhD on pinkeye, gave a very engaging and thought provoking presentation via video conference. The presentation covered diagnosis, causes and treatments, with many examples from his veterinary practice in the border area of Queensland and New South Wales. The talk prompted staff at the Arid Zone Research Institute (AZRI) to revisit local knowledge about pinkeye, where the conditions are so different. We started by conducting a survey with producers to capture more of their experience with pinkeye.

The regional pinkeye survey was well received with 28 responses indicating the high level of local interest in the issue.

Results of the survey

The results from the 2020 survey are:

  • 27 of the 28 responses were from producers with cattle south of Tennant Creek.
  • 15 of these saw pinkeye as a big issue on their place while 12 did not.
  • 11 producers said they noticed a particular breed was affected more than others. Five said Angus cattle and 6 said Herefords, providing some evidence that British breeds are more affected. Those producers that were less affected run other breeds - Charolais, Santa Gertrudis cross, Droughtmaster, Santa Gertrudis and Brahman.
  • 17 producers said no one breed was more affected.
  • Two properties had both Angus and Hereford cattle, with one recording Herefords as more susceptible while the other property said Angus.
  • Pinkeye infections were more common during the warmer months from September 2019 until April 2020, although the exact periods varied between properties. There did seem to be some parallels drawn with the abundance of flies, mustering times and dust.
  • The reported percentage of cattle affected with pinkeye ranged very widely, from 1 per cent to 40 per cent of the entire herd. Some producers said it was hard to estimate, especially for stations where infection was much higher in certain classes of cattle and lower in others.
  • Pinkeye was noted to be affecting weaners more than other age groups.
  • One comment was made that the practice of kicking dust at young animals to make them move in the yards is poor practice as it only increases the chance of the animal getting pinkeye.
  • Some producers also noted that they found it hard to know what pinkeye was and whether it may be cancer eye or something else.

Some of the actions producers have taken to lessen the prevalence of pinkeye are listed in the table below.

Adaption  on property to lessen the effect of pinkeye No. of  producers doing that
Change hay feeders 2
Pinkeye treatments 5
Good diet 2
Fly catchers 2
Breeding for eye pigmentation 2
Not leaving pools of water around for  flies to breed in 2
Not keeping cattle in the yards too long 3
Sprinkler systems in yards/water down  yards 5
Change type of hay 2
Clean dung out yards 1
Insect repellents on immunised herd bulls 1
Change trucking route to reduce dust 1
Sell infected cattle 1
Choose more tropically adapted cattle  breeds 2
Quarantine infected cattle where possible 2

Of the producers that did treat their cattle, topical treatments were the most common as listed below.

Treatment type No. of producers using
Eye patches 8
Terramycin spray 8
Orbenin eye ointment 9

Some producers used a combination of ointment and patches while others used treatments on their own.

We also spoke to our colleagues in Tennant Creek to see if they saw much pinkeye in the Barkly herds. They said they didn’t and suggested a few possible reasons. Firstly, the breeds up there are regarded as less susceptible to pinkeye. Also the cattle they inspect are normally mature, ready for sale and the disease is more likely to affect young cattle such as weaners.

So what causes pinkeye?

The primary cause of pinkeye is usually attributed to a bacterium, Moraxella bovis,and most research, treatment and prevention efforts have been directed against this organism. However, Dr Kneipp is investigating if M. bovis really is always involved. Ultimately, disease occurs when conditions to do with the infectious agents, the host (cattle) and the environmental come together to reach a ‘tipping point’. Dr Kneipp presented various important factors in his talk. Many of these came up in the producer survey and in discussion with local vets and researchers who also identified some other significant issues.

Pinkeye has been around for a long time and the general response is to treat it with patches, spray or ointment, or to leave animals to recover without treatment. A better understanding of how and why the disease occurs should help with identifying the best management options to minimise both the occurrence and the impacts.

Possible role of pestivirus

There is a possible link between pestivirus and pinkeye. Pestivirus is an immuno-suppressant disease which means that when animals are infected with pestivirus they are also more vulnerable to other diseases. Pestivirus is thought to go through herds in cycles which might occur every few years but sometimes more or less frequently. When it is less apparent in the herd, it is usually because most of the animals are immune to it. Pestivirus can have significant, negative production effects, especially when it hits a naive herd (one where all the animals are pestivirus free). If a pestivirus outbreak coincides with harsh environmental conditions like dry times, it could increase susceptibility to pinkeye.

The following observations support the idea of a link but do not prove it. The herd on Old Man Plains Research Station is pestivirus free and we have not had any significant issues with pinkeye. Another property in the Alice Springs district that had tested negative for pestivirus also didn’t have issues with pinkeye at the time.

Dr Jillian Kelly, a vet from Coonamble in NSW also believes there is link between pestivirus and pinkeye. “Pestivirus plays a big role. Drought feeding and early weaning (& congregation of animals) is a big factor too - both because of dust and transmission of eye bacteria but also because of pestivirus. If you've got persistently infected animals in the mob (they are germ factories).” So when she tests for pestivirus she also swabs eyes to see what bugs are present, in particular the bacteria that causes pinkeye, and to see if treatment is warranted.

Possible role of infectious bovine rhinotracheitis (IBR)

There is probably also a link between infectious bovine rhinotracheitis (IBR) virus and pinkeye. IBR is an acute, contagious respiratory disease in cattle caused by bovine herpesvirus type 1, commonly affecting the respiratory tract and reproductive system. Like pestivirus, IBR is an immuno-suppressant. In North America, IBR virus has been identified as contributing to the severity of pinkeye by weakening the cornea and making it more susceptible. In the Alice Springs district IBR is considered to be common and widespread and should definitely be considered as a possible factor in local pinkeye outbreaks.

Other risk factors that may have combined influence

There are several other factors that local vets and cattle researchers think are involved. Environmental and management factors that are likely to be important are: quality and quantity of feed, cattle condition, the way any hay is fed (with or without hay feeder), dust, flies, and how long cattle spend in the yards.

Cattle breeds almost certainly vary in the susceptibility to Pinkeye. Some local vets feel there is clear observational evidence of this, and the survey results also support it. Many stations in the district favour traditional British cattle breeds (Bos taurus) and some of these may be particularly susceptible to pinkeye. Brahmans (Bos indicus) and composite breeds with mixed B. indicus and B. taurus origins appear to be less susceptible.

More from Dr Kneipp on causes and treatments

Dr Kneipp believes that pinkeye is often misdiagnosed and that the issue may not always be caused by Moraxella bovis. Like our local vets, he strongly believes that multiple risk factors are often involved. Producers often diagnose issues themselves, but getting proper diagnosis can give them more information about what is really going on, which is important if you want to successfully manage pinkeye. Ensuring that cattle have adequate nutrition could be an important part of reducing risk of pinkeye. Likewise, minimising causes of irritation and trauma to the eye can help minimise pinkeye infections. Dr Kneipp also suggested that a Vitamin A injection may help with reducing the chance of pinkeye or similarly presenting issues. During droughts, cattle are often low in Vitamin A, as a consequence of dry feed. Low Vitamin A can present as runny eyes, which attracts flies. Dr Kneipp recommends starting with an accurate diagnosis rather than using vaccinations or injections as a ‘first port of call’ treatment. You need to work out what combination of issues may be leading to the tipping point and clinical disease. Dr Kneipp also noted the lack of literature on pinkeye which is one of his motivations for doing a PhD on this condition.

Summary of factors in pinkeye outbreaks

The multiple factors discussed above can be grouped into 6 main ones that could be at play when pinkeye presents itself as a serious issue in the herd, as it did on some stations last summer:

  • Pinkeye bacteria (Moraxella bovis) or other bacteria (e.g. Mycoplasma sp.)
  • Other diseases that increase susceptibility to pinkeye (IBR & pestivirus)
  • Nutrition and general condition of stock
  • Environmental factors like land and pasture condition, dust, flies, irritants in hay (e.g. burrs, dust)
  • Eye trauma (scratches and penetration wounds from sticks when eating top feed or from stalks in coarse hay or remnant grass tussocks)
  • Breed – increased susceptibility of some European breeds.

With so many possible contributing factors, pinkeye can be quite a complex disease to manage. Effective treatment is challenging during large outbreaks on properties with large herds, especially if there is uncertainty about the diagnosis and contributing causes. Keeping records of outbreaks could help individual properties develop their approach to pinkeye prevention and management. If you get animals tested for pinkeye bacteria, pestivirus, or IBR, especially during an outbreak of pinkeye in your herd, we would really like to know about it. It could be a vital piece of the pinkeye puzzle.

Contacts

Arid Zone Research Institute
08 8951 8142

Meg Humphrys
Pastoral Extension Officer
08 8951 8144

meg.humphrys@nt.gov.au

Peter Saville
Principal Veterinary Officer
08 895 18181

peter.saville@nt.gov.au

Jocelyn Coventry
Pastoral Production Officer
08 8951 8142

jocelyn.coventry@nt.gov.au

Acknowledgements

Thank you to everyone that participated in the survey (between Tuesday 8 September and Tuesday 27 October 2020 online, and in person). If you were unable to fill in the survey but would still like to submit survey results you can do so at the following link https://www.surveymonkey.com/r/8G99R9V

A special thanks to Dr Jillian Kelly, District Veterinarian for Central West Local Land Services in Coonamble, and Dr Mac Kneipp, a practising vet based in Goondiwindi, for their comments and insight given in the article. If you would like to know more about Dr Kneipp’s work on pinkeye his PhD should be complete in the next year with more written literature to come out of it.

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