RESUMEN
A serological study was conducted with calves experimentally infected with the protozoan parasite Neospora caninum. The animals were inoculated with either a low or high dose of N. caninum tachyzoites and temperature responses monitored daily for the first 2 weeks after inoculation. Blood samples were collected before inoculation, and at regular intervals thereafter for 1 year. Serological analysis was achieved using an indirect fluorescent antibody test (IFAT), an enzyme-linked immunosorbent assay (ELISA) and an IgG avidity ELISA. Injection of Neospora produced a significant rise in rectal temperature in the high dose group. In addition, the lymph node draining the site of inoculation increased in size following injection in all animals, in both infected groups, before returning to normal by day 14 after injection. Both groups given N. caninum produced specific antibody that was detected by the IFAT and the ELISA, which remained elevated for the 12-month duration of the experiment. The specific Neospora antibodies produced did not cross-react in an IFAT for the detection of antibodies to Toxoplasma gondii. IgG avidity increased 2 weeks after inoculation, in both infected groups, until week 12 when infection was well established. There was a little difference between the two infected dose groups. This study demonstrates that the two different doses of N. caninum produced a similar antibody response, and that the higher dose also induced a febrile reaction. The IgG avidity ELISA was successful at distinguishing between recent and long-standing infection in this study. However, in both groups, there was fluctuation in the levels of specific antibody throughout the yearlong study, which accords with similar experiments in pregnant cattle, where it has been suggested that fluctuation may indicate periodic recrudescence of infection and a re-stimulation of antibody production by antigen.
Asunto(s)
Enfermedades de los Bovinos/parasitología , Bovinos/parasitología , Coccidiosis/veterinaria , Neospora/aislamiento & purificación , Animales , Anticuerpos Antiprotozoarios/sangre , Afinidad de Anticuerpos , Enfermedades de los Bovinos/sangre , Enfermedades de los Bovinos/inmunología , Coccidiosis/sangre , Coccidiosis/inmunología , Coccidiosis/parasitología , Ensayo de Inmunoadsorción Enzimática/veterinaria , Femenino , Técnica del Anticuerpo Fluorescente Indirecta/veterinaria , Inmunoglobulina G/sangre , Masculino , Neospora/inmunología , Estudios Prospectivos , Distribución Aleatoria , Toxoplasma/inmunología , Toxoplasma/aislamiento & purificaciónRESUMEN
Three groups of eight pregnant sheep were inoculated with tachyzoites of the NCl isolate of Neospora caninum at 45 (group 1), 65 (group 2) or 90 (group 3) days' gestation. A further six animals (group 4) served as controls. Fourteen of the infected ewes developed a fever, which in two cases was biphasic. In six ewes in group 1, the fetuses died and were resorbed, and in the other two the fetuses were aborted. In group 2, one ewe resorbed her fetus, six aborted dead fetuses and one produced a live lamb. In group 3, six ewes aborted and two produced one live and one stillborn lamb each. Thus, the stage of gestation influenced the outcome of infection. All but one of the ewes "seroconverted", as shown by enzyme-linked immunosorbent assay, and 10 of 13 fetal sera examined by an indirect immunofluorescent antibody test were positive. The polymerase chain reaction was also used to detect DNA of N. caninum in aborted tissues. Immunohistochemical examination showed that the parasite had invaded the placentas of all cases examined, displaying an apparent predilection for fetal chorionic epithelium and fetal placental blood vessels, as well as inducing thrombosis in some maternal caruncular blood vessels. Organisms were associated with fetal vasculitis, focal degeneration and inflammation of the chorioallantois, and widespread, severe focal necrosis in the placentome. Characteristic lesions were seen in the fetal brains, in addition to focal leucomalacia, thought to be due to anoxia resulting from the placental damage. The six control sheep in group 4 remained clinically healthy and produced normal uninfected lambs.
Asunto(s)
Coccidiosis/veterinaria , Neospora/patogenicidad , Complicaciones Parasitarias del Embarazo/veterinaria , Enfermedades de las Ovejas/etiología , Ovinos/parasitología , Animales , Anticuerpos Antiprotozoarios/análisis , Encéfalo/inmunología , Encéfalo/parasitología , Encéfalo/patología , Coccidiosis/etiología , Coccidiosis/patología , Cartilla de ADN/química , ADN Protozoario/análisis , Ensayo de Inmunoadsorción Enzimática/veterinaria , Femenino , Feto/inmunología , Feto/parasitología , Feto/patología , Inmunohistoquímica , Neospora/genética , Neospora/inmunología , Placenta/parasitología , Placenta/patología , Reacción en Cadena de la Polimerasa/veterinaria , Embarazo , Complicaciones Parasitarias del Embarazo/etiología , Complicaciones Parasitarias del Embarazo/patología , Resultado del Embarazo/veterinaria , Enfermedades de las Ovejas/patología , VirulenciaRESUMEN
In an initial experiment, 21 sheep in groups of five or six were inoculated subcutaneously (sc) with 10(8), 10(6) or 10(4) Neospora caninum tachyzoites (Liverpool isolate), or with control inoculum, and monitored for clinical signs and for "seroconversion". Animals given the two higher doses showed febrile responses and all three groups inoculated with the parasite showed seroconversion. In a second experiment, 12 pregnant sheep were each inoculated sc at 90 days' gestation with 10(6) tachyzoites, and at 25, 40 and 53 days post-inoculation (dpi) groups of four were killed for examination of the fetuses and placentas. Appropriate control ewes were included in the study. All fetuses were alive immediately before their dams were killed, except for one, which was found to be mummified at 40 dpi. Histopathological lesions were found consistently in both fetal central nervous system (CNS) and placental tissues. In the latter, focal necrosis, which was mild at 25 dpi, was much more severe at 40 dpi and much less severe at 53 dpi. Lesions in the fetal CNS consisted of focal microgliosis (with or without central necrosis), lymphoid cuffing and non-suppurative meningitis. Lesions were also found in fetal liver, heart and lung. Neospora antigen was demonstrated in fetal brain and placental tissues and, at 25 dpi, in single samples of fetal liver and heart. The prescapular lymph nodes did not differ in size from those of control fetuses but were more mature in that they contained a significantly greater number of secondary follicles. Both IgM and IgG antibodies to N. caninum were detected in the serum of fetuses from infected ewes. Thus, N. caninum readily infected pregnant ewes and caused lesions in fetal tissues and placentas which resembled those of ovine toxoplasmosis. In addition, the changes were similar to those of bovine neosporosis; the infected pregnant ewe therefore offers a good model for the bovine disease.
Asunto(s)
Neospora/patogenicidad , Infecciones Protozoarias en Animales , Animales , Anticuerpos Antiprotozoarios/análisis , Antígenos de Protozoos/inmunología , Temperatura Corporal , Encéfalo/patología , Femenino , Masculino , Neospora/inmunología , Placenta/patología , Embarazo , Infecciones por Protozoos/inmunología , Infecciones por Protozoos/parasitología , Infecciones por Protozoos/patología , Ovinos , Factores de TiempoAsunto(s)
Anticuerpos Antiprotozoarios/sangre , Enfermedades de las Ovejas/inmunología , Toxoplasma/inmunología , Toxoplasmosis Animal/diagnóstico , Vacunación , Animales , Anticuerpos Antiprotozoarios/aislamiento & purificación , Ensayo de Inmunoadsorción Enzimática , Femenino , Técnica del Anticuerpo Fluorescente Indirecta , Pruebas de Fijación de Látex , Sensibilidad y Especificidad , Ovinos , Toxoplasmosis Animal/inmunologíaRESUMEN
Decoquinate was tested for its ability to reduce the effect of experimentally induced toxoplasmosis in pregnant ewes. Sheep were given decoquinate in their feed daily at either 2 mg or 1 mg/kg bodyweight from 10 days before an oral challenge with Toxoplasma gondii oocysts at 90 days of gestation, until lambing. Feeding decoquinate at the higher rate caused a delay in the onset of the febrile response to infection, reduced the overall severity of the fever and delayed the production of antibodies to the parasite. This treatment also reduced the placental damage caused by the parasite, lengthened the mean gestation period and increased the number and weight of live lambs, in comparison with ewes not fed decoquinate but challenged with T gondii oocysts. The treatment with 1 mg of decoquinate had smaller effects.
Asunto(s)
Coccidiostáticos/administración & dosificación , Decoquinato/administración & dosificación , Enfermedades de las Ovejas/prevención & control , Toxoplasmosis Animal/prevención & control , Aborto Veterinario/epidemiología , Animales , Anticuerpos Antiprotozoarios/sangre , Peso al Nacer/efectos de los fármacos , Temperatura Corporal/efectos de los fármacos , Femenino , Placenta/patología , Embarazo , Ovinos , Enfermedades de las Ovejas/inmunología , Enfermedades de las Ovejas/patología , Toxoplasma/inmunología , Toxoplasmosis Animal/inmunología , Toxoplasmosis Animal/patología , Resultado del TratamientoRESUMEN
Sixteen sheep were inoculated subcutaneously over the left prefemoral lymph node with an abortifacient strain of Chlamydia psittaci. Groups of four animals were killed after 3, 6, 12 and 18 days. Four of eight sheep which received a control inoculum were killed on day 6 and four on day 18. The left and right prefemoral lymph nodes were removed and weighed and portions taken from each for examination by the polymerase chain reaction (PCR), by culture, and by histopathological and immunohistochemical methods. The left prefemoral lymph nodes enlarged after the injection of C. psittaci, with the group mean weight on day 6 being the greatest and that on day 18 being normal. Examination by "nested" PCR showed samples from these nodes to be positive, except for one animal killed on day 3 and one on day 12. Live organisms, however, were not cultured from any of the samples collected. C. psittaci antigen was detected immunohistochemically in three of four nodes on day 3, in each of four on day 6, and in two of four on both days 12 and 18. Nodes from the contralateral side remained normal, as did those from unchallenged control sheep, and no antigen or DNA was detected in them.
Asunto(s)
Antígenos Bacterianos/análisis , Chlamydophila psittaci/aislamiento & purificación , ADN Bacteriano/aislamiento & purificación , Lipopolisacáridos/análisis , Ganglios Linfáticos/microbiología , Psitacosis/veterinaria , Enfermedades de las Ovejas/microbiología , Animales , Anticuerpos Antibacterianos/inmunología , Anticuerpos Monoclonales/inmunología , Secuencia de Bases , Chlamydophila psittaci/inmunología , Femenino , Técnicas para Inmunoenzimas , Ganglios Linfáticos/patología , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Psitacosis/microbiología , Psitacosis/patología , Ovinos , Enfermedades de las Ovejas/patologíaRESUMEN
The kinetics of interferon gamma (IFN gamma) production in vivo was examined in sheep during a primary and secondary infection with the sheep vaccine strain (S48) of Toxoplasma gondii. Efferent lymph plasma from a node draining the site of inoculation was tested for anti-viral activity which could be neutralized with monoclonal antibodies against IFN gamma. Within 2 to 5 days of primary infection IFN gamma was detected in each of five sheep and persisted for 6 to 9 days. Accelerated production of IFN gamma occurred after secondary infection, the cytokine being detected in the first 24 h, and persisting in lymph for a further 4-5 days. From day 6 onwards after primary infection, efferent lymph cells produced IFN gamma when stimulated in vitro with a crude T. gondii antigen. These results show that IFN gamma is induced in sheep after infection with the S48 strain of T. gondii.
Asunto(s)
Interferón gamma/biosíntesis , Enfermedades de las Ovejas/inmunología , Toxoplasma/inmunología , Toxoplasmosis Animal/inmunología , Animales , Interferón gamma/metabolismo , Cinética , Linfa/inmunología , Vacunas Antiprotozoos/inmunología , Ovinos , Enfermedades de las Ovejas/metabolismo , Enfermedades de las Ovejas/prevención & control , Toxoplasmosis Animal/metabolismo , Toxoplasmosis Animal/prevención & controlRESUMEN
The kinetics of induction of T cell responses were examined in efferent lymph from a node draining the site of a primary inoculation of Toxoplasma gondii. The numbers of T cells increased after infection, due initially to an expansion of the CD4+ T cell population followed by an increase in the number of CD8+ T cells which coincided with the peak lymphoblast response. Proliferative responses of CD4+ T cells to T. gondii antigen were detectable from day six after infection and immune efferent lymph cells inhibited the intracellular multiplication of T. gondii in vitro. Optimum inhibition was achieved using CD8+ T cells restimulated in vitro, and the effector function appeared to be directed preferentially against the autologous rather than the allogeneic infected target cell. The results provide unique information on the induction of immune responses to T. gondii in vivo and provide evidence that both CD4+ and CD8+ T cells are necessary for the development of protective immunity induced by the S48 strain of T. gondii which is used as a live vaccine in sheep.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/inmunología , Enfermedades de las Ovejas/inmunología , Toxoplasmosis Animal/inmunología , Enfermedad Aguda , Animales , Antígenos de Protozoos/inmunología , Línea Celular , Vías Eferentes , Femenino , Fibroblastos/parasitología , Inmunofenotipificación/veterinaria , Ganglios Linfáticos/citología , Ganglios Linfáticos/inmunología , Ganglios Linfáticos/parasitología , Activación de Linfocitos/inmunología , Recuento de Linfocitos , Ovinos , Enfermedades de las Ovejas/parasitología , Toxoplasma/crecimiento & desarrollo , Toxoplasma/inmunologíaRESUMEN
Efferent lymphatic cannulation was used to study the dissemination of strain S48 of Toxoplasma gondii and the cell output from the prefemoral lymph node, after infection of both "naive" and vaccinated sheep. In the former the mean cell output decreased for 3 days before reaching a peak at 11 and 12 days, but in vaccinated ewes a similar drop in cell output and subsequent peak occurred significantly earlier, at 24 h and 5 days, respectively. The cellular response in both types of sheep was largely due to a marked increase in blast cells. The detection of live toxoplasms and parasite DNA by mouse inoculation and the polymerase chain reaction, respectively, gave similar results; the parasite was demonstrated in lymph from days 3 to 12 during a primary infection but with a sharp cut-off after day 9 coinciding with the peak blast cell response. Very little evidence of T. gondii was found in lymph of vaccinated sheep after challenge. Immunity, which is thought to be largely T-cell mediated and is sustained without continuous antigenic stimulation, suppresses dissemination of the parasite in the lymph and therefore to other sites, which might include the gravid uterus.
Asunto(s)
Linfa/citología , Vacunas Antiprotozoos/administración & dosificación , Enfermedades de las Ovejas/patología , Toxoplasma , Toxoplasmosis Animal/patología , Animales , Femenino , Linfa/parasitología , Linfa/fisiología , Recuento de Linfocitos , Ovinos , Enfermedades de las Ovejas/parasitología , Enfermedades de las Ovejas/prevención & control , Toxoplasma/inmunología , Toxoplasma/aislamiento & purificación , Toxoplasmosis Animal/parasitología , Toxoplasmosis Animal/prevención & controlRESUMEN
Sheep can be immunised against toxoplasma abortion with a live vaccine composed of S48 tachyzoites. In this study the immunity induced in sheep was examined 18 months after vaccination. Seventy-three sheep were divided into three groups. Group 1 was vaccinated and 18 months later, when they were 90 days pregnant, the 27 sheep were challenged orally with Toxoplasma gondii oocysts. These ewes produced significantly more live lambs, after a significantly longer gestation period, than the 34 unvaccinated, challenged ewes in group 2. In addition there was less placental damage and fewer lambs were born with antibody to the parasite in the vaccinated group than in group 2. The 12 ewes in group 3 served as unvaccinated, unchallenged control animals. The degree of protection induced by the S48 tachyzoites was as good 18 months after vaccination as previously observed six months after vaccination.
Asunto(s)
Aborto Veterinario/inmunología , Vacunas Antiprotozoos , Enfermedades de las Ovejas/inmunología , Toxoplasma/inmunología , Toxoplasmosis Animal/inmunología , Vacunación/veterinaria , Animales , Anticuerpos Antiprotozoarios/inmunología , Femenino , Embarazo , Resultado del Embarazo/veterinaria , OvinosRESUMEN
Experimentally induced toxoplasmosis in pregnant ewes was treated with a combination of sulphamezathine and pyrimethamine. Fifteen untreated ewes gave birth to 14 live and six dead lambs whereas all the 15 lambs born to the 12 treated ewes were viable. The placental lesions were less severe, the gestation period was longer and the precolostral antibody titres to Toxoplasma gondii were lower, all significantly, for the lambs born to the treated ewes.
Asunto(s)
Complicaciones Parasitarias del Embarazo/veterinaria , Pirimetamina/uso terapéutico , Enfermedades de las Ovejas/tratamiento farmacológico , Sulfametazina/uso terapéutico , Toxoplasmosis Animal/tratamiento farmacológico , Animales , Anticuerpos Antiprotozoarios/aislamiento & purificación , Quimioterapia Combinada , Femenino , Inmunoglobulina G/aislamiento & purificación , Inmunoglobulina M/aislamiento & purificación , Embarazo , Complicaciones Parasitarias del Embarazo/tratamiento farmacológico , Complicaciones Parasitarias del Embarazo/inmunología , Ovinos , Enfermedades de las Ovejas/inmunología , Toxoplasma/inmunología , Toxoplasmosis Animal/inmunologíaRESUMEN
An epidemic of acute, disseminated toxoplasmosis caused 30 per cent mortality and an apparent 100 per cent morbidity in a captive colony of squirrel monkeys (Saimiri sciureus). The source of the infection could not be elucidated. Although most deaths were due to pulmonary oedema, one monkey probably died of heart and liver failure. These findings support the view that New World monkeys are unusually sensitive to Toxoplasma gondii infection. The similarity of the disease in these monkeys with that in immunocompromised human beings is an observation worthy of further investigation.