Friday, August 8, 2008

Parasites: The Good, the Bad, the Not-So-Ugly

The Good: These photos were taken a day or so apart. They show a cabbage worm on a kale leaf, paralyzed and parasitized by tiny cocoon-forming wasps. We had an outbreak of the cabbage worms, then noticed many scenes like this with the caterpillar slowly being drained of life force by the parasites. Some farms purchase such beneficial wasps and release them to try to control pests. I just put out a banquet of a variety of plants for them, and invited them to come, and they did.

We also noticed a few aphids starting to colonize the kale a few weeks ago. These tiny pests can spread at an incredible speed. But on close examination we noticed many of the swollen, gold-sheened ones that have been parasitized by even tinier wasps. Again, just establishing a fairly natural environment has brought these helpful wasps to our farm of their own volition. And we haven't seen the expected outbreak of aphids at all.

Sometimes parasites are our friends. Sometimes they aren't.


The Bad: We lost a lamb last week to complications of internal parasites...4-S syndrome, for starters. That stands for "Sick Sheep Seldom Survive". By the time you notice they're sick, they are on Death's doorstep and you really have to work hard to bring them around.

The first-born lamb this season has been a problem since Day One. Malpresentation at birth resulted in a very weak lamb, slow start, intensive care for days. Probably he did not get an adequate dose of colostrum in those critical first hours. Then he was rejected by Mom, therefore bottlefed. The bottle-feeders were inexperienced and not very careful about following instructions, I later learned. We made a lot of mistakes while figuring out how I could balance the off-farm job with lambs in chronic special care. So his early nutrition left a lot to be desired, and he's been the runtiest lamb of the year.

At our last worming, nearly 2 weeks ago, he was clearly suffering from parasites, probably haemonchus ("barber pole worms" because they are part red, part white)--a nematode that sucks nutrient-rich blood from the stomach lining, and in sufficient numbers can literally bleed an animal to death internally. The increasingly severe anemia in the earlier stages of infestation manifests as pale "pink parts" on sheep that have them (nose pad, ears, armpits, rectum/vulva--wherever there isn't wool and the skin isn't pigmented), pale gums, and the whites of the eye losing the brownish tint and fine veins that characterize a healthy sheep. The anemia can result in edema, with fluids especially collecting under the throat to form a swollen "bottle jaw"--a classic sign of worm infestation, but one that can fluctuate drastically throughout the day. An infested sheep may also have diarrhea, be reluctant or unable to stand or move, and have droopy ears and a general depressed demeanor.

#211 had all of these symptoms at worming. Badly.

I put him in a pen with some of the other ram lambs that have gotten so big that they are likely to breed their mothers if left together much longer. The guys are in the pen east of the back yard, rotating into the back yard sometimes for grazing, so it's easy to keep watch on them.

After worming, he got worse--not unusual. The stress of handling often puts a borderline sheep "over the edge". We did special "supportive care" as best we could, considering my work schedule and everal volunteers being on vacation at the time. "Pig iron" (iron dextran) and B vitamin injections to combat anemia and boost appetite. A quiet pen alone. The best, choicest fresh grass and lambsquarters from parasite-free areas of the garden. Alfalfa pellets. Tubed him with electrolytes (Gatorade for sheep) to combat dehydration in hot weather. Nutri-drench vitamin and mineral supplement. Once again, his care derailed a lot of progress on other things around the farm.

He seemed to rally and improved a lot. But then he took a turn for the worse, and he started to have labored breathing. Before we had time to consult with the vet, he was dead, probably from inhalation pneumonia associated with the tube feeding or Nutri-drench. Sad, but it happens. We struggle every summer to keep the barber pole worms under control, but they are an ugly, ugly foe, and some individuals are more sensitive than others.


Not So Ugly: Not quite a parasite, but so beautiful I had to include this very fuzzy, inadequate photo of a beetle we found today. The book gives its common name as "Caterpillar Hunter" so apparently it is It was easy to catch: dead on the circle drive in the woods. Not how I like to collect specimens. Even if it were in focus, the still, two-dimensional shot would hardly convey the incredibly brilliant, scintillating iridescent green of the wings and deep lapis blue of the thorax.

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