2002 - Nasal Bots
Seem to Defy the Miracle Herb Garlic
Since acquiring my first sheep back in 1992, I have never used chemical treatments to control internal parasites. The organic methods described in these pages have worked very well for me, and after all these years SkyLines sheep still remain virtually free of internal parasites (as evidenced by regular fecal tests performed by my vet). However, this one stumped me . . .
Respiratory Infections? During the winter of 2002, nearly all of the SkyLines sheep exhibited symptoms that I originally thought might be respiratory infections, but later discovered were caused by nasal bots (the larvae of the oestrus ovis species of fly). I dug into the subject, and subsequently learned more about this little fly than I ever really wanted to know.
According to my research, in mid-late summer (while the sheep are out in the pastures) this industrious little fly lays her eggs in or near the sheep's nostrils, and when the eggs hatch they crawl into the sheep's nasal passages to grow. They spend the winter maturing in that nice warm, moist environment, and their presence irritates the tissues to the point of causing that clear mucus discharge. Yuck!
With a nasal bot infestation, the sheep is not actually sick, and there's usually no fever or loss of appetite. But, she's uncomfortable, the discharge can lead to a hacking cough, and the constant irritation can set up an environment in which a bacterial infection can gain a foothold. It's just not a good situation and it needs to be dealt with in order to keep the sheep in optimal health.
Garlic just didn't cut
it as a treatment
The infestation was over, but I had to assume it would repeat itself the following winter if I didn't do something. Here's where it really pays to develop a good working relationship with your veterinarian. (I've worked with Dr. Dan Brown of The Animal Clinic in Moscow ID since 1998. He's wonderful.)
Dr. Dan and I spent the summer researching treatments for nasal bots. He spent quite a bit of time on the phone with his former professors at Washington State University School of Veterinary Medicine, and we both also scoured the web for further information. We finally had to conclude that the only effective treatment we could find for this particular type of fly infestation was Ivomec. Ug.
Bring on the Drugs
Wow! By winter of 2003-2004, only two ewes had exhibited the classic runny nose symptoms that nearly the entire flock had experienced previously. One treatment of Ivomec drench cleared up the problem with these two girls immediately, and nobody else appeared to have been infected.
Caveat: Of course, it's also possible that garlic had nothing to do with this at all. Maybe 2003 was simply a bad year for the oestrus ovis species of fly, or maybe another aspect of my management program somehow upset their reproductive cycle. Time will tell. I'll do the mid summer garlicking again next year and keep you updated.
Winter 2004 was the same thing as the previous year - 2 ewes showing nasal bot symptoms out of 70 sheep total. I treated these infected sheep with one dose of Ivomec and the symptoms cleared up within days. Nobody else showed any symptoms all winter. Progress! I'll continue the mid-summer garlic treatments and keep you posted.
The flies are still around though . . . My extra mid-summer garlic treatment does seems to be nearly eliminating the nasal bots themselves, but so far I can't see that it's done anything to reduce the number of pesky flies that torment the sheep during the hottest part of the summer. Using IPM (Integrated Pest Management) techniques like releasing parasitic wasps may be great for reducing flies in a barnyard area that's heavily laden with manure, but it just seems impractical to purchase and release enough of them for this entire 60+ acre property where the sheep move from one pasture to another on a daily or weekly basis...
Winter '06-'07 Update -
I hesitate to go out on a limb and say the garlic is responsible for reducing the total number of flies and hence the nasal bot infestation - there could easily be other factors at work such as the natural rise and fall of insect population groups. But I'll be continuing my mid-summer garlic treatments for a few years anyway. And of course, I'm always open to new information on the subject . . .