Naegleria fowleri is a single-celled living organism (otherwise known as an amoeba) that is capable of infecting humans, usually when water containing the amoeba is taken in through the nose. Commonly found in warm freshwater lakes, rivers, hot springs and soil, these amoebas travel up from the nose into the brain where it begins to destroy brain tissue, however (thankfully!) you cannot be infected by drinking contaminated water. Naegleria fowleri was first identified in South Australia but is found all over the world, and is one of more than 20 species of Naegleria, though it is the only one which is known to infect humans. Infections are rare but often fatal.
Image: US Centre for Disease Control and Prevention
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Wormcasts are podcasts produced by ParaBoss covering parasite management topics — worms, flies, lice, ticks and fluke — for sheep, cattle and goats.
by Deb Maxwell, ParaBoss Executive Officer
While the northern, summer-rainfall producers are well used to barber’s pole worm (Haemonchus contortus), their southern*, winter-rainfall brethren have less experience with this blood-sucking worm. But 2021 will likely be the “Year of southern barber’s pole worms” with clinical disease shaping up to be more widespread than has been seen for many a year.
If you are in a more typical southern Australian scour worm region and your property has had a little to a lot more summer rainfall than usual, barber’s pole worms may have flourished, and the more significant rainfall events that have occurred over summer (greater than 10 mm within a period of a week), the worse the problem will be. The worm larvae that hatched during these warmer, rainy periods survive on the pasture for many months—even through frosts—and sheep will progressively ingest more worms, building an ever-increasing burden for some time. Review of past monthly reports indicates a problem could appear well into autumn and early winter.
*Areas referred to as “southern” are typically at a latitude further south than Sydney in the eastern states, and anywhere in the farming areas of South Australia and Western Australia.
This past summer has been a bad season for flystrike in areas which experienced high rainfall and mild temperatures. This is because conditions in these areas were perfect for the Australian sheep blowfly, Lucilia cuprina, which thrives on mild, humid weather.
The female blowfly searches for susceptible sheep, attracted by sheep odours and particularly fleece-rot damage in damp fleece. Females will then lay up to 300 eggs into the fleece. Under the perfect conditions these eggs can hatch within eight hours, but typically within a day. The maggots feed on the sheep for three to five days before dropping off and burrowing into the ground to pupate. In warm conditions, they will pupate in soil for another seven to nine days, emerging as an adult within about 12 days. In cooler weather, with soil temperatures below 15 degrees, the pupae will survive over-winter in the soil waiting for more favourable conditions, which can lead to a population boom in spring if the flies encounter susceptible sheep after emerging.
Though an adult fly may only live for several weeks, they can lay a batch of up to 300 eggs every four to eight days. This means fly populations can rise very quickly in favourable conditions and where susceptible sheep are present. Given that a density of seven to ten flies per hectare can cause significant numbers of strikes, and that struck sheep will continue to be targeted by flies, proper management is vital to ensuring the welfare of the sheep and breaking the life cycle of the fly.
Preventing flystrike through management strategies and chemical treatments, as well as treating struck sheep, can go a long way to reducing the flystrike risk on your property. Find out more via www.flyboss.com.au.
Treating and eradicating lice infestations can be a costly and time-consuming process. Lice themselves can impact the value of wool and limit production, with effects building up over time. Previous editions of ParaBoss News earlier in the year have discussed prevention strategies to keep lice out of your flock, recognising that strategies to prevent introduction will often provide significant returns on those investments. However, we know that no biosecurity plan is entirely foolproof, and lice may still make their way on to your property.
LiceBoss have developed a Treatment Decision Guide for producers which can help to make decisions on how to treat sheep that are known or suspected to have lice. The Guide steps through the pertinent information about your individual situation on-farm and what you know about your lice status. With enough information, the Guide presents a series of recommendations on whether to proceed with a treatment, including information on how to properly check for lice, whether to shear, what types of treatment to use and options for how to apply that treatment.
While the LiceBoss Treatment Decision Guide has been developed to provide a quick and easy reference point, it cannot replace professional advice that is specific to your property.
Like people getting sick, some goats are better at shrugging off a worm burden to continue growing and developing. We call this resilience, characterised by goats showing less ill effects from worms. But did you know that some goats are more resistant to worms that others? This means that their immune systems are better at preventing worms from growing in the gut and limiting the number of eggs produced by established worms. Worm resistance is a trait for which goats can be bred, by selecting breeding goats based on their worm resistance.
For those familiar with Estimated Goat Breeding Values (EBV), which are an estimate of the animal’s genetic merit, a worm egg count (WEC) EBV can be used to select bucks with a better than average resistance, which is determined by consistently lower WEC results. Of course, the best possible WEC EBV result will need to be balanced with other genetic traits which are important to you and which you are trying to breed for.
Over time, a focused breeding strategy can increase the resistance of your herd to worms, meaning fewer eggs will be deposited on pastures, slowing the growth and spread of worm populations and reducing the number of drenches you use throughout the year.
ParaBoss News is produced with support
from Animal Health Australia