Laboratory 5
SPIRURIDS AND FILARIDS
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Card 5:1
| Spirocerca lupi The esophageal worm of dogs. These worms are large and usually coiled. Living specimens are pink to bright red in color. |
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Card 5:2
| Spirocerca lupi The eggs of this worm are small (40 X 15 um), oval, thick shelled with parallel sides. When passed in the feces they contain a larva bent in the shape of an "U". Some students have told us that these look like miniature paperclips. |
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Card 5:3
| Spirocerca lupi Mounted specimen showing the esophageal lesion caused by the worm. Note the fibrous nodule or tumor with the worms coiled inside. Tissues in these nodules have been known to undergo malignant transformation. |
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Card 5:4
| Spirocerca lupi Radiographs
Note the granulomatous mass surrounding the esophagus (difficult to see here) in both the general survey and in the angiogram on the right. Also note that in the survey you can see the thickening of the bodies of the thoracic vertebrae (red arrows). The angiogram clearly shows an aneurysm in the descending aorta. |
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Card 5:5
| Dracunculus insignis This is an adult spirurid worm removed from a dog. This parasite of wildlife lives subcutaneously in its host. The female worm will make a hole through the skin (usually of the leg) in order to deposit L1 when the skin gets wet. |
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Card 5:6
| Dracunculus insignis This slide shows the L1 of the "guinea worm" of wildlife. This is the stage that is infective to the intermediate host, Cyclops sp. If a tube of water is placed over the skin ulcer formed by the female worm, L1 will be discharged into the tube and can be used to diagnose the infection. |
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| This slide shows the adult female worm discharging L1 into a test tube. |  . |
Card 5:7
| Dirofilaria immitis These worms are found mainly in the pulmonary arteries and, with heavy infections, in the right atrium. Females reach a size of 25-30 cm long, and are slender. Males are shorter (12-16 cm) and the tail (right) is spirally coiled. |
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Card 5:8
| Dirofilaria immitis - microfilaria
Note the tapered anterior end. In most specimens you will see a straight body and straight (or slightly curved) tail. The width is > 6 um. From a Knott preparation. |
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Card 5:8a
| Dirofilaria immitis Ultrasound showing caval syndrome. Numerous white spots can be seen in the uppermost section. These spots represent adult worms in the right ventricle. |
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Card 5:8b
| Dirofilaria immitis Ultrasound showing two adult worms in the pulmonary arteries. The presence of the worms is easily identified. Each worm is seen as parallel white lines. |
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Card 5:9
| Dipetalonema reconditum
microfilaria Note the "blunt" anterior end (the cephalic hook may or may not be seen). The tail is curved (usually). The width (4.7 to 5.8 um) is less than D. immitis. |
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Card 5:10
| Dirofilaria immitis Microfilariae stained by the acid phosphatase technique. NOTE that staining is "zonal". These zones correspond to the excretory (anterior) and anal (posterior) pores of the microfilariae. |
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Card 5:11
| Dipetalonema reconditum Microfilaria stained by the acid phosphatase technique. Note that the staining is uniform in these microfilariae. |
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Card 5:12
| Females of Aedes aegypti mosquitoes feeding on blood containing microfilariae of Dirofilaria immitis via artificial membrane feeding apparatus. |  . |
Card 5:13
| Digestive tract of blood-engorged female Ae. aegypti. A: Midgut with blood. B: Hindgut (may be pulsating). C: Malphigian tubules (white in color). Note: You can actually see the giant 1o cells of the tubules under the dissecting scope. |
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Card 5:14
| Gut contents of female Ae. aegypti showing microfilariae of D. immitis. |
Card 5:15
Larvae of D. immitis from malphigian tubules 6 days after infection.
(Focus up and down).
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Card 5:16
| Third stage larvae (infective) in mouthparts (labial sheath) 13 days after infection. |  |
| Arrows point to emerging L3 from proboscis. |  |
Card 5:17
| This museum specimen is from a dog with D. immitis infection. The pulmonary arteries have been dissected open to reveal the primary predilection site of the adult parasite. This museum specimen also shows adults of D. immitis in the right atrium. Retrograde movement of large numbers of adults into the right heart, as seen here, is usually an artifact of death, but may occur in vivo in cases of caval syndrome. |  . |
Card 5:18
| This model depicts the primary predilection site of adult D. immitis - the pulmonary arteries. Note that the model also represents the formation of rough villus-like plaques in the arterial lining, a response to injury by the worms and the primary lesion responsible for pulmonary hypertension in heartworm disease. |  . |
Card 5:19
| This model depicts D. immitis adults in the right atrium of the canine heart. Such a situation may occur in caval syndrome when decreased cardiac output permits retrograde migration of adult worms from the pulmonary arteries. In many cases, finding adult worms in this location at necropsy is simply an artifact of death. When pulmonary blood flow ceases, the worms move into the right heart. |  . |
Card 5:21
| Onchocerca lienalis - microfilariae from a bovine skin biopsy
To see the microfilariae, carefully remove the petri dish top and focus on the bottom of the dish. The worms often congregate around the edges of the dish or around the skin biopsy itself. They are tiny, less than 300 um in length, and should be highly motile. Please do not readjust the microscope or light. |
Card 5:22
| Setaria equina Removed from the peritoneal cavity of a horse. Males: 4 to 8 cm. Females: 7 to 14 cm. |
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Card 5:23
| Setaria sp. microfilaria These microfilariae are sheathed. |
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Card 5:24
| Gongylonema pulchrum The sinusoidal tracks on the mucus membrane of this sheep's esophagus indicates where the adult of this spirurid worm is located. This worm uses dung beetles as the intermediate host. This nematode is a non-pathogenic parasite of many domestic mammals. |
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Card 5:25
| Physaloptera sp. These spirurid nematodes are parasites of the stomach of carnivores. They are normally found in opossums and raccoons but can occasionally be found in dogs and cats. This parasite uses a coprophagous beetle as an intermediate host. |
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Card 5:26
"Horse hair worms" Adult found in swimming pool
Adults are free living inhabitants of fresh water. Larvae are parasitic in insects. The larvae mature to the adult stage in the insect and when the insect is in contact with water the adult emerges. This is why the adult worm can be found swimming in a pet's water dish or the family swimming pool. |
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Card 5:27
| Review Question A dog was presented to a local veterinarian for a routine heartworm exam. The dog was not showing any clinical signs of infection. The results of a Knott concentration test are seen in the compound scope at the right. (Please do not move the specimen!) The results of a serologic test for Dirofilaria immitis antigen are also seen at this station. This test is showing a negative. A. Based on the information you have and on the appearance of the specimen under the scope, what would be your diagnosis? B. What further testing might you do to confirm your diagnosis? C. What are the implications of this finding for the dog's health? |
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