Pathology in Practice

Sarah E. Coe 1Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Martha Frances Dalton 1Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Eman Anis 2Veterinary Diagnostic and Investigational Laboratory, University of Georgia, Tifton, GA 31793.
3Department of Virology, Faculty of Veterinary Medicine, University of Sadat, Sadat City, Egypt 32511.

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Rebecca P. Wilkes 2Veterinary Diagnostic and Investigational Laboratory, University of Georgia, Tifton, GA 31793.

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Elizabeth W. Howerth 1Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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History

A 22-month-old female pygmy goat had a 1-day history of vocalization and a dark red vulvar discharge. The goat was pregnant and 1.5 months from gestational term. Abdominal ultrasonography revealed a small amount of anechoic fluid in the uterus, and no fetal heartbeat was detected. The following day, the doe aborted 2 fetuses, which were submitted along with the shared fetal membranes for postmortem examination.

Gross Findings

At necropsy, the fetuses and shared fetal membranes were diffusely dark brown, autolyzed, and partially desiccated (partial mummification; Figure 1). The fetuses were of unequal size; their crown-to-rump lengths were 14 cm and 10 cm. The cotyledons associated with the smaller fetus were approximately half the size of the cotyledons associated with the larger fetus. Internally, the body cavities did not contain fluid and the organs were shrunken and partially desiccated. Fetal membranes and tissues from each fetus were fixed in neutral-buffered 10% formalin, and additional fresh samples were obtained for ancillary testing.

Figure 1—
Figure 1—

Gross photograph of 2 aborted pygmy goat fetuses and their shared fetal membranes. Both fetuses are mummified and autolyzed. Notice the variation in size of the fetuses and corresponding variation in cotyledon size. Abortion occurred approximately 1.5 months prior to gestational term.

Citation: Journal of the American Veterinary Medical Association 256, 2; 10.2460/javma.256.2.183

Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page→

Histopathologic and Microbial Findings

Sections of fetal membranes and the brain, liver, kidneys, heart, lungs, and gastrointestinal tract of both fetuses were examined microscopically; all tissues were diffusely autolyzed and pale staining. The surface of the cotyledons was ulcerated and covered by necrotic cellular debris, and the underlying parenchyma contained multifocal areas of necrosis with infiltrating macrophages and mineralization (Figure 2). Occasional large gram-positive rods, smaller gram-negative rods, and gram-positive cocci arranged in short chains were scattered along the superficial aspect of the cotyledons. The liver, lung, kidney, and brain tissues had multiple foci of necrosis infiltrated with macrophages (Figure 3). Foci of necrosis in the liver were often mineralized. The epicardium was expanded by mononuclear inflammatory cells with infiltration into the myocardium.

Figure 2—
Figure 2—

Photomicrograph of a section of a cup-shaped cotyledon from the expelled fetal membranes. The surface is ulcerated and covered by necrotic cellular debris (arrows). There is multifocal necrosis with streaks of purple-stained mineralization (arrowheads) throughout the cotyledon. H&E stain; bar = 2 mm.

Citation: Journal of the American Veterinary Medical Association 256, 2; 10.2460/javma.256.2.183

Figure 3—
Figure 3—

Photomicrograph of a section of the brain from 1 of the 2 aborted fetuses. Notice the focus of necrosis infiltrated by macrophages. H&E stain; bar = 100 μm.

Citation: Journal of the American Veterinary Medical Association 256, 2; 10.2460/javma.256.2.183

Aerobic microbial culture of fetal membrane tissue resulted in growth of Klebsiella pneumoniae, Leclercia adecarboxylata, and Enterobacter spp. No anaerobic organisms were isolated from anaerobic microbial culture of fetal membrane tissue. Fluorescent antibody assays for Leptospira spp, Toxoplasma gondii, Listeria monocytogenes, and Chlamydophila spp were performed on samples of the fetal membranes, lungs, and liver of both fetuses; all test results were negative. A targeted next-generation sequencing (NGS) panel (developed by one of the authors [RPW]) to detect ruminant pathogens was performed on pooled fetal membranes and liver from both fetuses and yielded positive results for T gondii and K pneumoniae.

Rabbit anti-T gondii antibodiesa were applied to sections of fetal membranes and brain, liver, kidney, and heart tissues from both fetuses. Sections were exposed to diaminobenzidine chromogen and then counterstained with hematoxylin. Mononuclear inflammatory cells and necrotic debris within the necrotic foci in the fetal membranes, liver, and brain were positive for T gondii antigen; occasional stained tachyzoites were identified (Figure 4).

Figure 4—
Figure 4—

Photomicrograph of a section of a cotyledon from the expelled fetal membranes following immunohistochemical staining for Toxoplasma gondii. The necrotic focus in this section has intense immunopositivity for T gondii. Toxoplasma gondii-specific immunohistochemical stain, diaminobenzidine chromogen, and hematoxylin counterstain; bar = 50 μm.

Citation: Journal of the American Veterinary Medical Association 256, 2; 10.2460/javma.256.2.183

Morphologic Diagnosis and Case Summary

Morphologic diagnosis: severe, chronic, multifocal necrotizing and histiocytic placentitis in a pygmy goat doe and epicarditis, myocarditis, encephalitis, hepatitis, nephritis, and pneumonia, with mineralization and immunopositivity for T gondii, in twin fetuses with shared fetal membranes.

Case summary: abortion in a pygmy goat attributable to T gondii infection with concurrent K pneumoniae infection with fetal autolysis and partial desiccation.

Comments

For the doe and 2 fetuses of the present report, the microscopic, microbiologic, targeted NGS panel, and immunohistochemical findings were consistent with abortion attributable to concurrent infection with T gondii and K pneumoniae. Cats are the definitive host for T gondii, and the organism is transmitted to goats (or other intermediate hosts) via ingestion of food or water contaminated with cat feces containing oocysts.1 There are 3 life stages of T gondii: tachyzoites (individual form), bradyzoites (in tissue cysts), and sporozoites (in oocysts).2,3 The tachyzoites penetrate the host cell membrane and exist in vacuoles to withstand host immune defense mechanisms. Tachyzoites then replicate to form an intracellular tissue cyst. When these tissue cysts are ingested by cats, the walls of the cysts are destroyed in the stomach, and the bradyzoites are released and penetrate the epithelium of the small intestine and develop asexual schizonts.2 The schizonts release merozoites that form male and female gametes. The female gamete is fertilized by the male gamete, and the oocyst develops. The oocyst is released into the lumen of the intestines when the epithelial cells rupture, resulting in infective feces.3 Follow-up information from the owner of the goat revealed that cats had access to the goat's enclosure and bedding, which likely explained the origin of infection.

Toxoplasma gondii is a known cause of abortion in goats when an immunologically naïve, pregnant doe is infected. Depending on the stage of gestation when the doe is infected, possible adverse outcomes for a fetus are resorption, fetal death, mummification, or birth of a weak kid.4,5 Abortion of the fetus occurs because of necrosis of the placentomes.5 If a goat herd is housed in an area with a large population of cats, the rate of abortion can be high.

The characteristic gross lesion in abortion cases attributable to infection of the doe with T gondii is fetal membranes with dark red cotyledons that have multifocal white flecks of necrosis and calcification on the surface. The intercotyledonary portion of the fetal membranes typically appears normal or may have mild edema.4 These lesions were not observed in the shared fetal membranes of the fetuses of the present report because of marked autolysis of the tissues. Severe autolysis and mummification that complicates visualization of gross lesions during necropsy of aborted fetuses and fetal membranes is very common. It is also often extremely difficult to identify histopathologic lesions in aborted fetuses. However, despite the severe autolysis of the fetuses of the present report, lesions typical of toxoplasmosis were detected histologically in cotyledons and fetal tissues, calling into question the negative result of fluorescent antibody testing for Leptospira spp, T gondii, L monocytogenes, and Chlamydophila spp. Subsequently, a targeted NGS panel was used on pooled samples of fetal membranes and liver of both fetuses and was helpful in identifying the presence of T gondii and confirming detection of K pneumonia, the latter having been cultured during routine microbiologic testing. Toxoplasma gondii infection was further confirmed on the basis of results of immunohistochemical analysis of sections of placenta, liver, and brain tissues from both fetuses. Therefore, when there are no gross or histopathologic lesions identified in a fetus in an abortion case, use of a targeted NGS panel for identification of potential causative agents should be considered. The particular targeted NGS protocol used in the case described in the present report incorporated primers for all known common causes of abortion in ruminants. Infection of the doe of the present report with K pneumoniae was likely a confounding factor, given that such an infection rarely causes abortion in small ruminants. Klebsiella pneumoniae is a commensal organism in the intestines of small ruminants, and heavily soiled bedding can serve as a reservoir for the bacteria.6

Toxoplasma gondii has zoonotic potential for spread of protozoal disease, so fetal membranes and tissues should be handled with care.7 There are several other causes of abortion in goats that have zoonotic potential; therefore, aborted goat fetus necropsies should be performed in a biosafety cabinet.

Abortions in goats may also be caused by other infections with zoonotic potential, such as infections with Coxiella burnettii, Chlamydophila abortus, and Brucella melitensis, although the latter organism is not currently encountered in the United States.7 Owners should be directed to wear gloves when handling aborted tissues and thoroughly sanitize the area in which the tissues were found. If an abortion occurs on pasture, the owners should be encouraged to move pregnant animals to a different pasture or area and dispose of (eg, burn or bury) aborted fetuses and fetal membranes in an acceptable manner.7 Milk and meat from animals that abort should be processed appropriately (eg, pasteurization of milk and thorough cooking of meat) to ensure they are safe for human consumption.2,7

Results of serologic assessments, immunohistochemical analyses, or molecular techniques (eg, PCR assays) applied to appropriate samples from does and aborted fetuses can be used to diagnose toxoplasmosis.7 Infected animals can be treated with sulfadimidine and pyrimethamine. Careful attention should be paid to the required withdrawal period for drugs used for treatment in food-producing animals. These drugs may be beneficial in the early stage of the disease but will not eliminate the infection entirely.2 Interruption of the life cycle of T gondii is also very important for disease control. To prevent toxoplasmosis in a goat herd, cats should not be allowed to defecate in areas where goats may be feeding. Cats should also be kept out of areas where grain and hay are stored.7

Footnotes

a.

A gift from Dr. David Lindsay, Virginia-Maryland College of Veterinary Medicine, Virginia Tech University, Blacksburg, Va.

References

  • 1. Frenkel JK, Dubey JP, Miller NL. Toxoplasma gondii in cats: fecal stages identified as coccidian oocysts. Science 1970;167:893896.

  • 2. Dubey JP, Lindsay DS. Neosporosis, toxoplasmosis, and sarcocystosis in ruminants. Vet Clin North Am Food Anim Pract 2006;22:645671.

  • 3. Dubey JP, Frenkel JK. Cyst-induced toxoplasmosis in cats. J Protozool 1972;19:155177.

  • 4. Dubey JP, Miller S, Desmonts G, et al. Toxoplasma gondii-induced abortion in dairy goats. J Am Vet Med Assoc 1986;188:159162.

  • 5. Mobini S. Infectious causes of abortion. In: Youngquist RS, Threlfall WR, eds. Current therapy in large animal theriogenology. 2nd ed. St Louis: Elsevier, 2007;575584.

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  • 6. Christensen BW, McNabb BR, Troedsson MHT, et al. Diseases of the reproductive system, miscellaneous bacterial abortions. In: Smith BP. Large animal internal medicine. 5th ed. St Louis: Elsevier Mosby, 2015;14151416.

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    • Export Citation
  • 7. Edmondson MA, Roberts JF, Baird AN, et al. Theriogenology of sheep and goats. In: Pugh DG, Baird AN. Sheep and goat medicine. 2nd ed. Maryland Heights, Mo: Elsevier/Saunders, 2012;150230.

    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Gross photograph of 2 aborted pygmy goat fetuses and their shared fetal membranes. Both fetuses are mummified and autolyzed. Notice the variation in size of the fetuses and corresponding variation in cotyledon size. Abortion occurred approximately 1.5 months prior to gestational term.

  • Figure 2—

    Photomicrograph of a section of a cup-shaped cotyledon from the expelled fetal membranes. The surface is ulcerated and covered by necrotic cellular debris (arrows). There is multifocal necrosis with streaks of purple-stained mineralization (arrowheads) throughout the cotyledon. H&E stain; bar = 2 mm.

  • Figure 3—

    Photomicrograph of a section of the brain from 1 of the 2 aborted fetuses. Notice the focus of necrosis infiltrated by macrophages. H&E stain; bar = 100 μm.

  • Figure 4—

    Photomicrograph of a section of a cotyledon from the expelled fetal membranes following immunohistochemical staining for Toxoplasma gondii. The necrotic focus in this section has intense immunopositivity for T gondii. Toxoplasma gondii-specific immunohistochemical stain, diaminobenzidine chromogen, and hematoxylin counterstain; bar = 50 μm.

  • 1. Frenkel JK, Dubey JP, Miller NL. Toxoplasma gondii in cats: fecal stages identified as coccidian oocysts. Science 1970;167:893896.

  • 2. Dubey JP, Lindsay DS. Neosporosis, toxoplasmosis, and sarcocystosis in ruminants. Vet Clin North Am Food Anim Pract 2006;22:645671.

  • 3. Dubey JP, Frenkel JK. Cyst-induced toxoplasmosis in cats. J Protozool 1972;19:155177.

  • 4. Dubey JP, Miller S, Desmonts G, et al. Toxoplasma gondii-induced abortion in dairy goats. J Am Vet Med Assoc 1986;188:159162.

  • 5. Mobini S. Infectious causes of abortion. In: Youngquist RS, Threlfall WR, eds. Current therapy in large animal theriogenology. 2nd ed. St Louis: Elsevier, 2007;575584.

    • Search Google Scholar
    • Export Citation
  • 6. Christensen BW, McNabb BR, Troedsson MHT, et al. Diseases of the reproductive system, miscellaneous bacterial abortions. In: Smith BP. Large animal internal medicine. 5th ed. St Louis: Elsevier Mosby, 2015;14151416.

    • Search Google Scholar
    • Export Citation
  • 7. Edmondson MA, Roberts JF, Baird AN, et al. Theriogenology of sheep and goats. In: Pugh DG, Baird AN. Sheep and goat medicine. 2nd ed. Maryland Heights, Mo: Elsevier/Saunders, 2012;150230.

    • Search Google Scholar
    • Export Citation

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