Quiz: Re-Emerging Infectious Diseases in Dogs

Babesia spp are piroplasms and protozoal parasites of the family Apicomplexa that parasitize erythrocytes. Babesia spp appear in many different morphologies, including the signet ring as seen in Figure 2.^1-2

Hemotropic mycoplasmas are epicellular cocci that also parasitize erythrocytes; however, the appearance of this signet ring is suggestive of a piroplasm rather than a coccus. Further, Mycoplasma spp are epierythrocytic parasites (ie, they attach to the outer cell membrane of the RBC), whereas Babesia spp are found inside the RBC; this differentiation can be difficult, as Mycoplasma spp superimposed on RBCs may appear to be in the cytosol.

Howell-Jolly bodies are basophilic, intracellular inclusions that consist of remnant nucleic acid. They generally result from inappropriate erythropoiesis. Morphologically, they appear deep blue and round. (Figure 3, red arrow)

Bartonellaspp are gram-negative intracellular cocci that infect erythrocytes and may appear similar toMycoplasmaspp (Figure 3, black arrows) on blood smear, although bacteremia is rare and organisms often are not found on cytology.

Babesia spp are piroplasms and protozoal parasites of the family Apicomplexa that parasitize erythrocytes. Babesia spp appear in many different morphologies, including the signet ring as seen in Figure 2.^1-2

Hemotropic mycoplasmas are epicellular cocci that also parasitize erythrocytes; however, the appearance of this signet ring is suggestive of a piroplasm rather than a coccus. Further, Mycoplasma spp are epierythrocytic parasites (ie, they attach to the outer cell membrane of the RBC), whereas Babesia spp are found inside the RBC; this differentiation can be difficult, as Mycoplasma spp superimposed on RBCs may appear to be in the cytosol.

Howell-Jolly bodies are basophilic, intracellular inclusions that consist of remnant nucleic acid. They generally result from inappropriate erythropoiesis. Morphologically, they appear deep blue and round. (Figure 3, red arrow)

Bartonellaspp are gram-negative intracellular cocci that infect erythrocytes and may appear similar toMycoplasmaspp (Figure 3, black arrows) on blood smear, although bacteremia is rare and organisms often are not found on cytology.

Babesia spp are piroplasms and protozoal parasites of the family Apicomplexa that parasitize erythrocytes. Babesia spp appear in many different morphologies, including the signet ring as seen in Figure 2.^1-2

Hemotropic mycoplasmas are epicellular cocci that also parasitize erythrocytes; however, the appearance of this signet ring is suggestive of a piroplasm rather than a coccus. Further, Mycoplasma spp are epierythrocytic parasites (ie, they attach to the outer cell membrane of the RBC), whereas Babesia spp are found inside the RBC; this differentiation can be difficult, as Mycoplasma spp superimposed on RBCs may appear to be in the cytosol.

Howell-Jolly bodies are basophilic, intracellular inclusions that consist of remnant nucleic acid. They generally result from inappropriate erythropoiesis. Morphologically, they appear deep blue and round. (Figure 3, red arrow)

Bartonellaspp are gram-negative intracellular cocci that infect erythrocytes and may appear similar toMycoplasmaspp (Figure 3, black arrows) on blood smear, although bacteremia is rare and organisms often are not found on cytology.

Babesia spp are piroplasms and protozoal parasites of the family Apicomplexa that parasitize erythrocytes. Babesia spp appear in many different morphologies, including the signet ring as seen in Figure 2.^1-2

Hemotropic mycoplasmas are epicellular cocci that also parasitize erythrocytes; however, the appearance of this signet ring is suggestive of a piroplasm rather than a coccus. Further, Mycoplasma spp are epierythrocytic parasites (ie, they attach to the outer cell membrane of the RBC), whereas Babesia spp are found inside the RBC; this differentiation can be difficult, as Mycoplasma spp superimposed on RBCs may appear to be in the cytosol.

Howell-Jolly bodies are basophilic, intracellular inclusions that consist of remnant nucleic acid. They generally result from inappropriate erythropoiesis. Morphologically, they appear deep blue and round. (Figure 3, red arrow)

Bartonellaspp are gram-negative intracellular cocci that infect erythrocytes and may appear similar toMycoplasmaspp (Figure 3, black arrows) on blood smear, although bacteremia is rare and organisms often are not found on cytology.

Both B gibsoni, which is found worldwide, and B conradae, found in southern California and parts of the southern United States, are small intraerythrocytic piroplasm parasites (3 m in diameter) that cannot be distinguished by cytology alone. In contrast, larger Babesia spp (eg, B canis, B rossi, B vogeli) are typically 4-5 m in diameter.¹

Both B canis (formerly B canis subsp canis), found mostly in southern Europe adjacent to the Mediterranean, and B vogeli (formerly B canis subsp vogeli), another worldwide parasite that primarily inhabits southern Europe, are large piroplasms. B rossi (formerly B canis subsp rossi), another large piroplasm, is found in subSaharan Africa.¹

Both B gibsoni, which is found worldwide, and B conradae, found in southern California and parts of the southern United States, are small intraerythrocytic piroplasm parasites (3 m in diameter) that cannot be distinguished by cytology alone. In contrast, larger Babesia spp (eg, B canis, B rossi, B vogeli) are typically 4-5 m in diameter.¹

Both B canis (formerly B canis subsp canis), found mostly in southern Europe adjacent to the Mediterranean, and B vogeli (formerly B canis subsp vogeli), another worldwide parasite that primarily inhabits southern Europe, are large piroplasms. B rossi (formerly B canis subsp rossi), another large piroplasm, is found in subSaharan Africa.¹

Both B gibsoni, which is found worldwide, and B conradae, found in southern California and parts of the southern United States, are small intraerythrocytic piroplasm parasites (3 m in diameter) that cannot be distinguished by cytology alone. In contrast, larger Babesia spp (eg, B canis, B rossi, B vogeli) are typically 4-5 m in diameter.¹

Both B canis (formerly B canis subsp canis), found mostly in southern Europe adjacent to the Mediterranean, and B vogeli (formerly B canis subsp vogeli), another worldwide parasite that primarily inhabits southern Europe, are large piroplasms. B rossi (formerly B canis subsp rossi), another large piroplasm, is found in subSaharan Africa.¹

Both B gibsoni, which is found worldwide, and B conradae, found in southern California and parts of the southern United States, are small intraerythrocytic piroplasm parasites (3 m in diameter) that cannot be distinguished by cytology alone. In contrast, larger Babesia spp (eg, B canis, B rossi, B vogeli) are typically 4-5 m in diameter.¹

Both B canis (formerly B canis subsp canis), found mostly in southern Europe adjacent to the Mediterranean, and B vogeli (formerly B canis subsp vogeli), another worldwide parasite that primarily inhabits southern Europe, are large piroplasms. B rossi (formerly B canis subsp rossi), another large piroplasm, is found in subSaharan Africa.¹

Both B gibsoni, which is found worldwide, and B conradae, found in southern California and parts of the southern United States, are small intraerythrocytic piroplasm parasites (3 m in diameter) that cannot be distinguished by cytology alone. In contrast, larger Babesia spp (eg, B canis, B rossi, B vogeli) are typically 4-5 m in diameter.¹

Both B canis (formerly B canis subsp canis), found mostly in southern Europe adjacent to the Mediterranean, and B vogeli (formerly B canis subsp vogeli), another worldwide parasite that primarily inhabits southern Europe, are large piroplasms. B rossi (formerly B canis subsp rossi), another large piroplasm, is found in subSaharan Africa.¹

The combination of azithromycin and atovaquone is the treatment of choice for small Babesia spp infection. The mechanism of action is not completely known but is suspected to result from inhibition of nucleic acid synthesis.^2-4

Imidocarb dipropionate is an antibabesial compound that leads to denaturation of DNA and decreased DNA replication. It has strongest efficacy in the treatment of large Babesia spp infections but would be suboptimal for the treatment of small Babesia spp infections.

Clindamycin and metronidazole can be used in combination to treat refractory cases of small Babesia spp infections but is not recommended as first-line therapy.

Meglumine antimoniate is an antimonial compound used in combination with allopurinol to inhibit replication of Leishmania spp organisms, but it has no effect on Babesia spp.

The combination of azithromycin and atovaquone is the treatment of choice for small Babesia spp infection. The mechanism of action is not completely known but is suspected to result from inhibition of nucleic acid synthesis.^2-4

Imidocarb dipropionate is an antibabesial compound that leads to denaturation of DNA and decreased DNA replication. It has strongest efficacy in the treatment of large Babesia spp infections but would be suboptimal for the treatment of small Babesia spp infections.

Clindamycin and metronidazole can be used in combination to treat refractory cases of small Babesia spp infections but is not recommended as first-line therapy.

Meglumine antimoniate is an antimonial compound used in combination with allopurinol to inhibit replication of Leishmania spp organisms, but it has no effect on Babesia spp.

The combination of azithromycin and atovaquone is the treatment of choice for small Babesia spp infection. The mechanism of action is not completely known but is suspected to result from inhibition of nucleic acid synthesis.^2-4

Imidocarb dipropionate is an antibabesial compound that leads to denaturation of DNA and decreased DNA replication. It has strongest efficacy in the treatment of large Babesia spp infections but would be suboptimal for the treatment of small Babesia spp infections.

Clindamycin and metronidazole can be used in combination to treat refractory cases of small Babesia spp infections but is not recommended as first-line therapy.

Meglumine antimoniate is an antimonial compound used in combination with allopurinol to inhibit replication of Leishmania spp organisms, but it has no effect on Babesia spp.

The combination of azithromycin and atovaquone is the treatment of choice for small Babesia spp infection. The mechanism of action is not completely known but is suspected to result from inhibition of nucleic acid synthesis.^2-4

Imidocarb dipropionate is an antibabesial compound that leads to denaturation of DNA and decreased DNA replication. It has strongest efficacy in the treatment of large Babesia spp infections but would be suboptimal for the treatment of small Babesia spp infections.

Clindamycin and metronidazole can be used in combination to treat refractory cases of small Babesia spp infections but is not recommended as first-line therapy.

Meglumine antimoniate is an antimonial compound used in combination with allopurinol to inhibit replication of Leishmania spp organisms, but it has no effect on Babesia spp.

Although Aspergillus spp may cause chorioretinitis, these organisms are rarely found in the aqueous fluid. Thus, of the testing procedures listed, anterior chamber aqueocentesis would be the least appropriate test in this patient.

In suspected cases of aspergillosis, the Aspergillus spp antigen EIA test (MiraVista Diagnostics) can be performed on either urine or serum and has good sensitivity and specificity, although false-positive results can occur with related mycotic infections and supplementation of certain drugs or IV fluids.⁵

Urine culture is an inexpensive and specific test for diagnosing disseminated aspergillosis, but its sensitivity may vary depending on the organ involved.⁶

Lymph node cytology can have excellent specificity for fungal lymphadenitis when organisms are seen, but sensitivity is hampered by low burden of infection or lack of identification of fungal hyphae, which might require use of special stains.⁶

Vertebral body cytology can have excellent specificity for fungal diskospondylitis when organisms are seen, but sensitivity is hampered by low burden of infection or lack of identification of fungal hyphae, which (like for lymph node cytology) might require use of special stains. In addition, ultrasound-guided vertebral body aspiration, which is recommended over blind aspiration, can be technically challenging.⁶

Although Aspergillus spp may cause chorioretinitis, these organisms are rarely found in the aqueous fluid. Thus, of the testing procedures listed, anterior chamber aqueocentesis would be the least appropriate test in this patient.

In suspected cases of aspergillosis, the Aspergillus spp antigen EIA test (MiraVista Diagnostics) can be performed on either urine or serum and has good sensitivity and specificity, although false-positive results can occur with related mycotic infections and supplementation of certain drugs or IV fluids.⁵

Urine culture is an inexpensive and specific test for diagnosing disseminated aspergillosis, but its sensitivity may vary depending on the organ involved.⁶

Lymph node cytology can have excellent specificity for fungal lymphadenitis when organisms are seen, but sensitivity is hampered by low burden of infection or lack of identification of fungal hyphae, which might require use of special stains.⁶

Vertebral body cytology can have excellent specificity for fungal diskospondylitis when organisms are seen, but sensitivity is hampered by low burden of infection or lack of identification of fungal hyphae, which (like for lymph node cytology) might require use of special stains. In addition, ultrasound-guided vertebral body aspiration, which is recommended over blind aspiration, can be technically challenging.⁶

Although Aspergillus spp may cause chorioretinitis, these organisms are rarely found in the aqueous fluid. Thus, of the testing procedures listed, anterior chamber aqueocentesis would be the least appropriate test in this patient.

In suspected cases of aspergillosis, the Aspergillus spp antigen EIA test (MiraVista Diagnostics) can be performed on either urine or serum and has good sensitivity and specificity, although false-positive results can occur with related mycotic infections and supplementation of certain drugs or IV fluids.⁵

Urine culture is an inexpensive and specific test for diagnosing disseminated aspergillosis, but its sensitivity may vary depending on the organ involved.⁶

Lymph node cytology can have excellent specificity for fungal lymphadenitis when organisms are seen, but sensitivity is hampered by low burden of infection or lack of identification of fungal hyphae, which might require use of special stains.⁶

Vertebral body cytology can have excellent specificity for fungal diskospondylitis when organisms are seen, but sensitivity is hampered by low burden of infection or lack of identification of fungal hyphae, which (like for lymph node cytology) might require use of special stains. In addition, ultrasound-guided vertebral body aspiration, which is recommended over blind aspiration, can be technically challenging.⁶

Although Aspergillus spp may cause chorioretinitis, these organisms are rarely found in the aqueous fluid. Thus, of the testing procedures listed, anterior chamber aqueocentesis would be the least appropriate test in this patient.

In suspected cases of aspergillosis, the Aspergillus spp antigen EIA test (MiraVista Diagnostics) can be performed on either urine or serum and has good sensitivity and specificity, although false-positive results can occur with related mycotic infections and supplementation of certain drugs or IV fluids.⁵

Urine culture is an inexpensive and specific test for diagnosing disseminated aspergillosis, but its sensitivity may vary depending on the organ involved.⁶

Lymph node cytology can have excellent specificity for fungal lymphadenitis when organisms are seen, but sensitivity is hampered by low burden of infection or lack of identification of fungal hyphae, which might require use of special stains.⁶

Vertebral body cytology can have excellent specificity for fungal diskospondylitis when organisms are seen, but sensitivity is hampered by low burden of infection or lack of identification of fungal hyphae, which (like for lymph node cytology) might require use of special stains. In addition, ultrasound-guided vertebral body aspiration, which is recommended over blind aspiration, can be technically challenging.⁶

Although Aspergillus spp may cause chorioretinitis, these organisms are rarely found in the aqueous fluid. Thus, of the testing procedures listed, anterior chamber aqueocentesis would be the least appropriate test in this patient.

In suspected cases of aspergillosis, the Aspergillus spp antigen EIA test (MiraVista Diagnostics) can be performed on either urine or serum and has good sensitivity and specificity, although false-positive results can occur with related mycotic infections and supplementation of certain drugs or IV fluids.⁵

Urine culture is an inexpensive and specific test for diagnosing disseminated aspergillosis, but its sensitivity may vary depending on the organ involved.⁶

Lymph node cytology can have excellent specificity for fungal lymphadenitis when organisms are seen, but sensitivity is hampered by low burden of infection or lack of identification of fungal hyphae, which might require use of special stains.⁶

Vertebral body cytology can have excellent specificity for fungal diskospondylitis when organisms are seen, but sensitivity is hampered by low burden of infection or lack of identification of fungal hyphae, which (like for lymph node cytology) might require use of special stains. In addition, ultrasound-guided vertebral body aspiration, which is recommended over blind aspiration, can be technically challenging.⁶

Fluconazole has excellent tissue penetration (including into the CNS), but because it is inactive against molds (eg, Aspergillus fundus organisms), this drug would be inappropriate in this patient.⁷

Randomized controlled trials in support of voriconazole treatment are lacking; however, veterinary case reports and literature from human medicine have supported empirical use of voriconazole as the treatment of choice. Likewise, randomized controlled trials supporting posaconazole treatment are lacking, but a recent case series has suggested partial efficacy in some dogs with disseminated aspergillosis.^7-9

Amphotericin B treatment has long been the standard of care in human medicine and is known to be fungicidal; however, its side effects (notably nephrotoxicity) sometimes limit its clinical use in dogs.⁷

Fluconazole has excellent tissue penetration (including into the CNS), but because it is inactive against molds (eg, Aspergillus fundus organisms), this drug would be inappropriate in this patient.⁷

Randomized controlled trials in support of voriconazole treatment are lacking; however, veterinary case reports and literature from human medicine have supported empirical use of voriconazole as the treatment of choice. Likewise, randomized controlled trials supporting posaconazole treatment are lacking, but a recent case series has suggested partial efficacy in some dogs with disseminated aspergillosis.^7-9

Amphotericin B treatment has long been the standard of care in human medicine and is known to be fungicidal; however, its side effects (notably nephrotoxicity) sometimes limit its clinical use in dogs.⁷

Fluconazole has excellent tissue penetration (including into the CNS), but because it is inactive against molds (eg, Aspergillus fundus organisms), this drug would be inappropriate in this patient.⁷

Randomized controlled trials in support of voriconazole treatment are lacking; however, veterinary case reports and literature from human medicine have supported empirical use of voriconazole as the treatment of choice. Likewise, randomized controlled trials supporting posaconazole treatment are lacking, but a recent case series has suggested partial efficacy in some dogs with disseminated aspergillosis.^7-9

Amphotericin B treatment has long been the standard of care in human medicine and is known to be fungicidal; however, its side effects (notably nephrotoxicity) sometimes limit its clinical use in dogs.⁷

Fluconazole has excellent tissue penetration (including into the CNS), but because it is inactive against molds (eg, Aspergillus fundus organisms), this drug would be inappropriate in this patient.⁷

Randomized controlled trials in support of voriconazole treatment are lacking; however, veterinary case reports and literature from human medicine have supported empirical use of voriconazole as the treatment of choice. Likewise, randomized controlled trials supporting posaconazole treatment are lacking, but a recent case series has suggested partial efficacy in some dogs with disseminated aspergillosis.^7-9

Amphotericin B treatment has long been the standard of care in human medicine and is known to be fungicidal; however, its side effects (notably nephrotoxicity) sometimes limit its clinical use in dogs.⁷