erythrocytes, transform into trophozoites, and multiply by binary fission to produce merozoites that undergo additional divisions or become larger, variably shaped gametocytes. 1 Pleomorphic organisms are most appreciable in large Babesia spp, including B
, the schizont stage of T uilenbergi and T luwenshuni is short, 11 whereas the merozoite stage is the most exposed stage to the host immune system. The purpose of the study reported here was to cultivate the merozoite stage of T uilenbergi for
culture was kept at 37°C in 5% carbon dioxide in air. Sarcocystis neurona merozoites were added to flasks of confluent BT cells. After 7 to 14 days of culture, most BT cells had lysed and released large numbers of merozoites into the medium. Cell debris
Objective—To determine clinical and pathologic findings before and after short-term (group 1) and longterm (group 2) treatment in dogs with Hepatozoon americanuminfection.
Animals—53 dogs with H americanuminfection.
Procedure—Medical records of dogs that were treated for hepatozoonosis diagnosed on the basis of meront or merozoite stages in skeletal muscle were reviewed.
Results—Circulating gametocytes of H americanum were identified in 12 of 53 dogs. Dogs were treated with various drugs, including toltrazuril, trimethoprimsulfadiazine, clindamycin, pyrimethamine, and decoquinate. Mean WBC counts prior to treatment were 85,700 and 75,200 cells/µl in groups 1 and 2, respectively, and 1 month after initiation of treatment were 12,600 and 14,600 cells/µl, respectively. Initial response to treatment was excellent in all dogs. Twenty-three of 26 dogs in group 1 relapsed at least once and died within 2 years; mean (± SD) survival time was 12.6 ± 2.2 months. Twenty-two of 27 group-2 dogs survived; 11 dogs had no clinical signs and were still receiving decoquinate (mean duration of treatment, 21 months), 11 dogs had no clinical signs after treatment for 14 months (range, 3 to 33 months; mean survival time, 39 months [range, 26 to 53 months]), 2 dogs were lost to follow-up, and 3 dogs were euthanatized because of severe disease.
Conclusions and Clinical Relevance—Although no treatment effectively eliminated the tissue stages of H americanum, treatment with trimethoprim-sulfadiazine, clindamycin, and pyrimethamine followed by long-term administration of decoquinate resulted in extended survival times and excellent quality of life. ( J Am Vet Med Assoc 2001;218:77–82)
(20 to 30 μm in diameter), which contained intra-cytoplasmic, basophilic, granular structures consistent with Cytauxzoon felis merozoites (0.75 to 2 μm in length; Figure 2 ). In the liver, monocytes containing similar merozoites were predominantly
Within the lamina propria of the small intestine, there was severe loss of crypts and large numbers of coccidial organisms (large schizonts that were 50 to 70 μm in diameter and contained merozoites measuring approx 1 × 2 μm) with necrosis
had spongiosis and contained increased numbers of microglial cells (microgliosis). Scant intra- and extracellular clusters of oval to crescent-shaped merozoites (approx 5 to 7 μm in length) were present in inflammatory foci, particularly those
organisms observed in the cytologic preparations. In addition, round to ovoid schizonts, approximately 10 μm in diameter with multiple internal 1- to 2-μm-long crescent-shaped merozoites, were present. Each merozoite had a small, round, eccentric basophilic
expanded by cytoplasmic coccidial organisms ( Figure 3 ). Most of these organisms were 15- to 20-µm-diameter schizonts containing multiple basophilic crescent-shaped merozoites. In addition, there were multiple 20-μm-diameter microgametes and macrogametes
immunocompetent horses 1 or in interferon-γ knockout mice, 2 even though the compound is active against S neurona in vitro. 3 An EPM vaccine based on homogenates of S neurona merozoites with conditional licensure has been marketed for prevention of EPM, but