White Eyes and Bottle Jaw: Are There Zebras?
Dr. Anne Zajac DVM, PhD, DACVM-Parasitology
Virginia-Maryland Regional College of Veterinary Medicine
Every veterinary student learns that when you hear hoofbeats you think of horses and not zebras—in other words, the most likely cause of disease in an animal is the most common one. The zebras are the unlikely causes of disease and should only be considered after the likely causes have been ruled out.
In most of the United States sheep and goat producers know that pale mucous membranes and bottle jaw signal the presence of a disease-causing load of the barber pole worm, Haemonchus contortus. But is Haemonchus the only cause of anemia and bottle jaw that you could encounter—could there be some zebras?
Anemia occurs when there is a reduction below normal in the number of red cells in the blood. In sheep and goats, the presence of anemia is best assessed by checking the color of the mucous membranes of the eye (easy to do with a FAMACHA© card, Figure 1).
Bottle jaw (Figure 2) is fluid accumulation (edema) that occurs in the intermandibular space (space between the two arms of the lower jawbone). Edema is caused by disruption of the normal balance of pressure and/or proteins between the blood and the spaces between cells located outside the blood vessels. This disruption can cause accumulation of fluid in the interstitial space (spaces between the cells of the tissues), which we see as edema.
Following infection of a sheep or goat with Haemonchus, the worms very quickly scratch the surface of the abomasum (stomach) with a sharp “tooth” and begin feeding on the blood released from small blood vessels. The amount of blood loss caused by a few worms is insignificant, but if the worms cause the loss of enough red cells and blood protein, the body gears up to replace them. But if too much blood is lost for too long a period, eventually the body can’t compensate adequately and the low level of red cells is visible as anemia. Sometimes, but not always, bottle jaw also develops because levels of protein in the blood also fall below normal and so more fluid stays in the interstitial spaces. We see that first in the area below the jaw. Whether or not bottle jaw develops in an individual depends on factors like the time course of infection.
WITHOUT QUESTION, THE MOST COMMMON CAUSE OF ANEMIA AND BOTTLE JAW IN SHEEP AND GOATS IN THE UNITED STATES IS THE BARBER POLE WORM!
But anemia and bottle jaw reflect low red cell and blood protein levels and there are some other causes. Most of these causes are rare compared to barber pole worm and some of them can be distinguished from haemonchosis because they produce other signs of disease as well.
Remember, however, that any other health problem could also be further complicated by worm infection. Here are some causes of anemia that might be seen by producers in the U.S. They can be grouped into a few major categories (Table 1):
For example, an animal attacked by predators that loses a large amount of blood will become anemic and remain so until red cells can be replaced. Traumatic anemia is unlikely to be confused with barber pole worm infection.
Another common parasite that could cause anemia is coccidia. Coccidiosis typically produces diarrhea, a sign not associated with barber pole worm. Anemia will develop only in severe cases as a result of extensive damage to the GI tract with loss of blood into the intestine.
In the Pacific Northwest and to a lesser degree the Gulf Coast region, sheep and goats can be infected with liver fluke (Fasciola hepatica). This parasite can cause poor condition, anemia and even death. Another fluke (Fascioloides magna) occurs in the Great Lakes region and Northeast but it usually produces disease that runs a shorter course so anemia may not have time to develop.
Anemia might occur with Johne’s Disease (paratuberculosis). This is a chronic wasting disease caused by bacteria. Anemia is not the primary sign of disease, but may be seen in addition to weight loss and possibly diarrhea.
There are a few other infectious diseases that could cause anemia but they are very rare or the anemia is accompanied by other signs like fever that allow them to be differentiated from barber pole worm.
Nutritional Causes of Anemia
The nutrient that has been associated with anemia in small ruminants most often is copper. Both copper deficiency and copper excess can result in anemia, although the mechanism of the anemia is different in each case. Copper deficiency can be caused by low levels of copper in the soil or by high levels of molybdenum and other substances that can bind copper and make it less available for use by the animal. There are many signs of copper deficiency in addition to anemia including poor appetite and growth, faded hair color, poor fleece, and musculoskeletal problems. The severity of the deficiency will determine which signs of disease develop.
Copper toxicity leads to rupture of red blood cells and usually appears as a rapid onset of weakness and depression, anemia, and acute death. Goats tolerate excess copper better than sheep. Copper toxicity occurs most often as a result of errors in mixing feed or feeding sheep minerals and premixes made for other livestock species. Sheep producers should check with their veterinarians before using copper oxide boluses for control of Haemonchus.
There are some other mineral imbalances that could lead to anemia, but they are less common than copper problems. Mineral imbalances in the soil are often regional and producers should consult local extension agents or other knowledgeable sources to find out if there are particular problems in their area. A few plants contain toxins that could cause anemia, especially in goats, most notably kale and other Brassica plants.
Anemia of chronic disease
Any animal species can develop what is known as “anemia of chronic disease”. This occurs when a chronic disease interferes with the normal ability to replace red blood cells. Even without blood loss, red blood cells have a definite life
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span and there is constant low level production of new cells. In a debilitated animal lost cells don’t get replaced. This could occur in chronic infectious disease conditions like Johne’s disease (mentioned above) or caseous lymphadenitis. Chronic malnutrition might also lead to decreased ability to make new red blood cells.
What about other causes of swelling below the jaw? Real bottle jaw rarely develops in the absence of anemia. Other possibilities for swelling in the space below the jaw are very unlikely. They include a severe insect or snake bite or an abscess in the neck could cause partial obstruction of a jugular vein. Increased blood pressure in the vein could cause edema in the head. A swollen lymph node might be mistaken for bottle jaw but would be more firm to the touch and would not be in the location directly under the jaw. Milk goiter, which occurs in young lambs, is swelling on the neck, not under the jaw.
So yes, there are some zebras when it comes to anemia and bottle jaw. However,
THE MOST COMMMON CAUSE OF ANEMIA AND BOTTLE JAW IN SHEEP AND GOATS IN THE UNITED STATES IS THE BARBER POLE WORM!
When you encounter anemia and bottle jaw in a small ruminant in almost all areas of the U.S. always approach it first as a parasite problem.
Here are some suggestions for when to start thinking about the zebras:
During the grazing season
If animals have access to grass for even a short period of the day assume anemia is from barber pole worm, treat the animal, and move it to a location where it will not be exposed to reinfection if at all possible.
However, if it is a very young animal (a few weeks) or there is no access to grass, barber pole worm is much less likely. It is OK to deworm, but you should take a fecal sample for a fecal egg count and confirm that your problem is worms.
If you have dewormed an animal with anemia/bottle jaw and there is no improvement in the animal’s condition or it deteriorates, three things could be happening:
1) Your dewormer isn’t working. There is so much drug resistance in barber pole worm that this is definitely the most likely explanation, even if you have used dewormers responsibly. The most common scenario is that the drug works partially, reducing the level of worms enough so that the sheep or goat doesn’t die, but not really allowing for a full recovery. Get a fecal sample for a fecal egg count to determine in a substantial number of parasites is still present.
2) You got rid of the worms, but the pasture is so contaminated that reinfection with a large number occurred right away, and there was no time for recovery before the next onslaught of blood feeders. Have a fecal egg count done, but remember that it will take about three weeks for the new worms to start producing eggs.
3) If you have effectively ruled out parasites as a problem and you still have anemia then you may have a zebra or another problem along with worms, for example worms complicated by Johne’s disease. Take a fecal sample and look for other signs of disease. Consult with your veterinarian.
Not during the grazing season:
If the affected animal is a ewe or doe within about 2 weeks of giving birth or in the first month after lambing/kidding the anemia/bottle jaw could be the result of arrested barber pole worm that has resumed development. Deworm and take a fecal sample for a fecal egg count to confirm that parasites are present.
If the affected animal is not periparturient and it is not Haemonchus transmission season and it is too late for leftover summer worms and too early for development of winter arrested larvae, then barber pole worm is less likely. Look for other signs of disease (fever, poor body condition, diarrhea, etc). Take a fecal sample for a fecal egg count. It will do no harm to deworm the animal, but if there is a low fecal egg count, this might be a zebra. Consult your veterinarian.
Table 1. Causes of Anemia and Bottle Jaw