Coccidiosis

To compare trimethoprim-sulfamethoxazole (TMP-SMZ) and vancomycin regarding efficacy and safety in the therapy of serious Staphylococcus aureus infections. Randomized, double-blind comparative trial. A tertiary-care hospital. One hundred and one intravenous drug users hospitalized with S. aureus infection. Cure and failure rates; blood and wound cultures; minimum inhibitory and bactericidal concentrations; serum inhibitory and bactericidal titers; temperature; leukocyte count; durations of treatment and hospitalization; and toxicity. Of 228 intravenous drug users, 101 had S. aureus infection and were included in the efficacy analysis (43 received TMP-SMZ and 58 received vancomycin). Methicillin-resistant S. aureus (MRSA) accounted for 47% of S. aureus isolates, and 65% of patients were bacteremic. Infections were cured in 57 of 58 vancomycin recipients and in 37 of 43 TMP-SMZ recipients (P less than 0.02). Failure occurred mostly in patients with tricuspid valve endocarditis and only in those with infection caused by methicillin-sensitive S. aureus (MSSA). The mean duration of bacteremia was 6.7 days in TMP-SMZ recipients and 4.3 days in vancomycin recipients. Among 222 subjects hospitalized for at least 24 hours, toxicity rates were similar for TMP-SMZ (23%) and vancomycin (20%) recipients; nausea and vomiting were associated with TMP-SMZ and inflammation at the intravenous site was associated with vancomycin. Forty-four percent of TMP-SMZ recipients and 29% of vancomycin recipients experienced side effects in the efficacy cohort (P greater than 0.05). Vancomycin is superior to TMP-SMZ in efficacy and safety when treating intravenous drug users who have staphylococcal infections. However, all treatment failures occurred in patients with MSSA infection at any site. Therefore, TMP-SMZ may be considered as an alternative to vancomycin in selected cases of MRSA infection.

Coccidiosis, an intestinal infection caused by intracellular protozoan parasites belonging to several different species of Eimeria, seriously impairs the growth and feed utilization of livestock and poultry. Host immune responses to coccidial infection are complex. Animals infected with Eimeria spp. produce parasite-specific antibodies in both the circulation and mucosal secretions. However, it appears that antibody-mediated responses play a minor role in protection against coccidiosis. Furthermore, there is increasing evidence that cell-mediated immunity plays a major role in resistance to infection. T lymphocytes appear to respond to coccidial infection through both cytokine production and a direct cytotoxic attack on infected cells. The exact mechanisms by which T cells eliminate the parasites, however, remain unclear. Although limited information is available on the intestinal immune system of chickens, gut lymphoid tissues have evolved specialized features that reflect their ro...

Two mixed-breed littermate dogs were fed mouse brains containing tissue cysts of the NC-beef isolate of Neospora caninum. Both dogs excreted N. caninum oocysts in their feces. Dog 1 which was given methylprednisolone acetate (MPA) prior to ingesting tissue cysts, excreted oocysts on days 5 to 10 inclusive and on day 17 after ingesting tissue cysts. Dog 1 had a serum antibody titer of 1 : 200 in the indirect fluorescent antibody test (IFAT) 35 days after it was fed tissue cysts. Dog 2, which was not treated with MPA, excreted oocysts on Day 6 and Day 9 after ingesting tissue cysts. Antibodies to N. caninum were not found in a 1 : 25 dilution of serum on any examination period for Dog 2 during the study. Neospora caninum was not found in the tissues of either dog by histological or immunohistochemical means following necropsy 42 days after being fed tissue cysts. The identity of the oocysts excreted in the feces of the dogs was confirmed by mouse inoculation studies.

An experiment was carried out to determine whether bovine colostrum or placenta could be a source of infection of Neospora caninum for dogs. For this purpose, two dogs were fed bovine colostrum to which culture-derived N. caninum tachyzoites were added and two other dogs were fed placental cotyledonary tissue from N. caninum seropositive cows. One dog served as a negative control during the start of the experiment but this control dog was fed cotyledonary tissue later on. None of the dogs did produce serum antibodies to N. caninum. All three dogs that were fed cotyledonary tissue did shed N. caninum oocysts, but no oocyst shedding was seen in the two dogs that were fed colostrum with N. caninum tachyzoites. Oocyst excretion did not resume in two dogs after repeated feeding of N. caninum infected placenta. The identity of the oocysts was confirmed by a bioassay in gerbils. It is concluded that ingestion of bovine placenta by dogs is an effective mode of transmission of N. caninum from cattle to dogs.

The gray wolf (Canis lupus) was found to be a new natural definitive host for Neospora caninum. Neospora-like oocysts were found microscopically in the feces of three of 73 wolves from Minnesota examined at necropsy. N. caninum-specific DNA was amplified from the oocysts of all three wolves. Oocysts from one wolf were infective for the gamma interferon gene knock out (KO) mice. Viable N. caninum (designated NcWolfUS1) was isolated in cell cultures seeded with tissue homogenate from the infected mouse. Typical thick walled tissue cysts were found in outbred mice inoculated with the parasite from the KO mouse. Tissue stages in mice stained positively with N. caninum-specific polyclonal antibodies. Our observation suggests that wolves may be an important link in the sylvatic cycle of N. caninum.

Studies were conducted to determine the pathogenic potential of the recently isolated bovine Neospora protozoa (BPA-1) for the bovine fetus. Cows chosen for study had Neospora titers < 160 using an indirect immunofluorescent antibody (IFA) test. Four experimental groups were studied. In group 1, 2 fetuses were inoculated in utero at 118 days gestation with culture-derived Neospora tachyzoites. A pregnant control cow was housed in the same pen, observed daily and screened serologically for evidence of exposure to Neospora. In group 2, 2 cows were infected with Neospora tachyzoites at 138 or 161 days gestation, and 1 control cow was given uninfected cell culture suspension simultaneously at 154 days gestation. Groups 3 (85 days gestation) and 4 (120 days gestation) each consisted of 2 cows infected with Neospora tachyzoites and 1 control cow given uninfected material at the same stage of gestation. Dead fetuses were surgically removed from the infected cows in group 1 on postinfect...

The effects of cyclosporin A (CsA) treatment and hormonal bursectomy on Eimeria tenella infection of chickens were investigated to evaluate the role of humoral antibody and cell-mediated immunity (CMI) in the host protective immunity to an intestinal protozoan disease, coccidiosis. Hormonal bursectomy had no significant effect on the host response to E. tenella. CsA treatment had a differential effect on the course of disease depending on how CsA was given relative to infection. Daily administration of CsA for 7 days beginning 1 day before primary infection with E. tenella enhanced disease resistance, whereas a single dose of CsA given before primary infection enhanced disease susceptibility compared with that of untreated controls. Chickens treated with CsA during the primary infection were resistant to reinfection at 5 weeks post-primary infection. Treatment of chickens immune to E. tenella with CsA at the time of secondary infection abrogated their resistance to reinfection despi...

We report the development of a real-time PCR assay for the quantitative detection of Neospora caninum in infected host tissues. The assay uses the double-stranded DNA-binding dye SYBR Green I to continuously monitor product formation. Oligonucleotide primers were designed to amplify a 76-bp DNA fragment corresponding to the Nc5 sequence of N. caninum . A similar method was developed to quantify the 28S rRNA host gene in order to compare the parasite load of different samples and to correct for the presence of potential PCR-inhibiting compounds in the DNA samples. A linear quantitative detection range of 6 logs with a calculated detection limit of 10 −1 tachyzoite per assay was observed with excellent linearity ( R 2 = 0.998). Assay specificity was confirmed by using DNA from the closely related parasite Toxoplasma gondii . The applicability of the technique was successfully tested in a variety of host brain tissues: (i) aborted bovine fetuses classified into negative or positive Neo...

Current serologic tests used to detect antibodies to Neospora caninum require species-specific secondary antibodies, limiting the number of species that can be tested. In order to examine a wide variety of animal species that may be infected with N. caninum, a modified direct agglutination test (N-MAT) similar to the Toxoplasma gondii modified direct agglutination test (T-MAT) was developed. This test measures the direct agglutination of parasites by N. caninum-specific antibodies in serum, thus eliminating the need for secondary host-specific anti-isotype sera. The N-MAT was compared to the indirect fluorescent-antibody test (IFAT) and the enzyme-linked immunosorbent assay (ELISA) with a "gold standard" serum panel from species for which secondary antibodies were available (n = 547). All positive samples tested were from animals with histologically confirmed infections. Up to 16 different species were tested. The N-MAT gave a higher sensitivity (100%) and specificity (97%...

Two overlapping cDNA clones (pBSCC-1 and pBSCC-2) bearing inserts ≈ 425 and ≈ 950 base pairs long, respectively, which are specific for bovine cholesterol sidechain cleavage cytochrome P-450 (P-450scc), have been identified by using two differential hybridization screening procedures followed by hybrid-selected RNA translation. By using these cloned cDNAs as hybridization probes, an RNA species was identified that had the properties expected of mRNA specific for P-450scc with respect to tissue specificity, corticotropin (ACTH)-mediated regulation of synthesis, and size of the protein product synthesized in vitro. In RNA samples obtained from bovine adrenal cortex, from bovine corpus luteum, and from cultured bovine adrenocortical cells, it was found that P-450scc is encoded by mRNA species ≈ 2000 bases long, a majority of which are polyadenylylated. P-450scc mRNA was not detected in RNA samples prepared from bovine heart, liver, and kidney. Treatment of cultured bovine adrenocortical cells with ACTH resulted in the appearance of elevated levels of P-450scc mRNA within 8 hr. Thus, ACTH promotes the enhancement of P-450scc gene transcription or acts to stabilize the transcripts. When pBSCC-2 cDNA was used to probe high molecular weight bovine DNA following treatment with restriction endonucleases, a simple pattern of hybridization was observed indicating that P-450scc may be encoded by a single gene.

The role of intestinal lymphocytes and gamma interferon (IFN-γ) production in protective immunity to Eimeria tenella infection was evaluated in two inbred strains of chickens (SC and TK) that display different patterns of susceptibility to coccidiosis. Oral inoculation of either strain with E. tenella led to parasite invasion of the intestinal cecum and cecal tonsils. Greater fecal oocyst shedding was seen in TK chickens. Flow cytometric analyses of cecal tonsil lymphocytes demonstrated greater numbers of CD4 + and T-cell receptor γδ-positive (TCR1 + ) cells in SC chickens and elevated numbers of CD8 + and TCR2 + cells in TK chickens following primary infection. IFN-γ mRNA expression was significantly increased in cecal tonsil and intraepithelial lymphocytes at days 6 and 8, respectively, after primary infection in SC compared to TK chickens. While no differences were noted between cecal tonsil lymphocytes of the two strains following secondary infection, TK chickens showed elevated...