The Nasal Bot Issue

2002 - Nasal Bots Seem to Defy the Miracle Herb Garlic
(News! Major progress has been made in dealing with bots -- check out Updates below)

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
Assuming the sheep had some sort of upper respiratory infection going on, I had tried the organic garlic approach all winter long, even tried antibiotics out of desperation, with no success at all. Then by spring, the sheep's noses dried up and all was well. (As I learned later, the larvae had matured and simply flown out of their cozy nest.)

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
I bit the bullet. In the fall of '02, I treated all the sheep (except the locker lambs) with Ivomec drench. Ivomec is one of several parasiticides used to treat internal parasites in sheep (I don't use it of course), but it's the only treatment recommended by vets for nasal bots. The winter following the Ivomec treatment nobody else turned up with the classic runny nose symptoms of nasal bot infestation. It seems the Ivomec did the job for winter '02-'03, but I wasn't happy about using it.


Winter '03-'04
During the summer of '03, I decided to try a new approach. I added another "garlicking" to the sheep's annual schedule, and treated them in mid-summer (July). My thought was that fresh garlic in the sheep's bloodstream might create a less hospitable environment for these industrious mamma flies to lay their eggs in. Or maybe the garlic would actually kill the eggs after she'd laid them . . . ?

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 '04-'05
I'm pretty encouraged about the nasal bot issue! It's been two summers now (2003 and 2004) during which I gave the sheep an extra garlic treatment in mid-summer.

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 '05-'06
This year I wintered 93 sheep total, and 6 of them turned up with severe nasal bot symptoms requiring Ivomec. It appears to be roughly the same percentage as previous years. I still think the additional mid-summer "garlicking" is helping, and I'll continue with it.

Winter '06-'07 Update - Hurrah!!
This winter I had to use Ivomec to treat nasal bots in only 3 sheep out of 95. Yay! This project has gone on for five years now, and I'm pleased with the results because I'm seeing a steady decline in the incidence of nasal bot infestation. I'm also seeing fewer instances of the sheep being bothered during the summer by flies hovering around their faces.

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 . . .

Winter '07-'08
I continued the mid-summer garlic treatment and there were no cases of the typical nasal bot-caused nasal discharge this winter (which I why I forgot to update this page until January 09:)

Winter '08-'09
Again, mid-summer garlic treatment and no cases of nasal bots this winter. Yippee! One less problem to deal with...

Final Caveat:
Please bear in mind that all of this information about my approach to controlling nasal bots (as well as internal parasites) is totally my own personal experience - "anecdotal" and not "science-based" information. As such, don't be surprised if some folks of a more skeptical mind boo-hoo the validity of my results and give you a hard time about your trying the garlic program. So be it - we organic farmers have been ridiculed for years anyway. Just use your own judgement and take from my experience whatever may be useful to you.




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SkyLines Farm 4551 Highway 6 Harvard, ID 83834
Purebred Romney & Romney-Cross Sheep