Neospora caninum in sheep: a herd case report

Neospora caninum was detected by means of PCR in the brain of 4 out of 20 aborted fetuses in a flock of 117 sheep exhibiting a persistent abortion problem, and N. caninum tissue cysts were furthermore found in encephalitic lesions in one of the PCR-positive fetuses. Toxoplasma gondii was detected as aborting agent in another 3 out of 20 fetuses. Antibodies to N. caninum (by indirect fluorescence antibody test (IFAT)) were found in 10.3% of 117 ewes and antibodies for T. gondii were found in 97.4% of 117 ewes. Other organisms associated with abortion were Chlamydia psittaci in three fetuses and Pasteurella multocida in one fetus. This is the first report of N. caninum associated abortion in naturally infected sheep.     

Transplacental Neospora caninum infection in dogs

A Beagle bitch was inoculated SC and IM with 1.5 million Neospora caninum tachyzoites on the 35th day of gestation. Eight pups were born alive 28 days after N caninum inoculation of the bitch. Pup 1 did not breathe and died while still enclosed in fetal membranes. Pup 2 died 2 days after birth (DAB). Pups 3, 4, and 5 were euthanatized on 2, 3, and 20 DAB, respectively, because they were hypothermic and not nursing. Pups 6, 7, and 8 remained clinically normal. Indirect fluorescent N caninum serum antibody titers were: less than 50 (pups 1 and 8 at 17 DAB, and the bitch before inoculation), 50 (pups 2 and 3 on 2 DAB), 200 (pups 6 and 7 on 17 DAB), and 800 (bitch on day 17 after parturition). Neospora caninum was recovered in cultured cells inoculated with placenta and tissues from all 5 pups necropsied, and N caninum was seen in histologic sections of the heart of pup 5. Results indicate that N caninum can be transplacentally transmitted in dogs.     

Neospora caninum infection in three dogs

Infection with Neospora caninum in three young dogs is described. The predominant clinical signs were lower motor neuron deficits of the pelvic limbs, bladder and rectum. In two cases there was liver infection and dysfunction. The younger dogs had an acute onset rapidly progressive syndrome. The older dog had a similar but more chronic course. The diagnosis was confirmed by an immunofluorescence antibody test. The parasite is sensitive to clindamycin and trimethoprim/sulphonamide preparations, however the prognosis for return to function is poor especially if muscle contracture has occurred.     

Serological investigation of aborted sheep and pigs for infection by Neospora caninum

Serology for Neospora caninum was undertaken using direct ELISAs on sera from 660 aborted sheep and 454 breeding sows, which had aborted or were considered infertile. All ovine sera were further tested by indirect fluorescent antibody test (IFAT) for N. caninum, and a latex agglutination test (LAT) for Toxoplasma gondii was performed on 423 of the samples, including all those positive by ELISA. ELISA-positive porcine sera were tested by IFAT and an inhibition ELISA for antibodies to N. caninum and by LAT for T. gondii. Only 3 (0.45%) of the ovine sera were seropositive for N. caninum by both ELISA and IFAT whereas although 40 porcine sera were seropositive by ELISA all were negative by IFAT. The results suggest that environmental exposure to N. caninum occurs rarely in sheep and pigs.     

Vaccine development against Neospora caninum infection

Neospora caninum is a recognized protozoan parasite of a wide range of mammalian hosts, and was reported for the first time in 1988. The isolation of its oocysts in dog's faeces in 1998 led to its establishment as a parasitic species undergoing typical coccidian life cycle. Infection with N. caninum causes paralysis and death in young livestock and companion animals, and is associated with abortions and stillbirth in cattle, and neurologic disease in calves. Considering the economic and agricultural importance of neosporosis, there is the urgent need to develop biological control measures aimed at preventing its transmission, infection, as well as reducing severity of the disease. In this paper, we have reviewed the progress made to date on the parasite-host immunology and on vaccine development including its prospects, and discussed possible strategies in the formulation of vaccine(s) against neosporosis.     

Disseminated infection with Neospora caninum in a ten-year-old dog

Naturally-occurring neosporosis with multiple organ involvement was identified in a 10-year-old neutered male Basset hound dog. Clinical signs were first noticed 3 weeks prior to referral and consisted of crouched stance and mild pelvic limb ataxia. Dexamethasone administration had provided transient improvement. On presentation to the teaching hospital, clinical signs included depression, pelvic limb ataxia, inability to stand without assistance, and pain on deep palpation of the cervical and lumbar vertebral column. Lesions were found in the myocardium, liver, spleen, adrenal glands, brain, and spinal cord. Tachyzoites of Neospora caninum were found in the myocardium and adrenal glands. Organisms stained with anti-Neospora caninum, but not to anti-Toxoplasma gondii serum in an immunohistochemical test.     

Diagnosis and treatment of Neospora caninum infection in a dog

Neospora caninum, a protozoan organism, caused extensor rigidity of the pelvic limbs in a 12-week-old dog. Diagnosis was based on results of muscle biopsy, neuroelectrodiagnostics, serotesting, and cell culture. Indirect fluorescent antibody (IFA) titer to N caninum was 1:800 at time of admission and 1:3,200 after 4 and 6 weeks. A reciprocal IFA titer of 50 to N caninum was also found in the CSF. Serotesting for T gondii was negative. Treatment with clindamycin followed by sulfadiazine and trimethoprim did not change the pelvic limb extensor rigidity, but other signs of minor neurologic dysfunction improved.     

Incidence and vertical transmission rate of Neospora caninum in sheep

The infection by Neospora caninum in sheep can lead to abortion and the birth of weak and debilitated lambs. The aim of this study was to assess the incidence of natural infection by Neospora caninum and the vertical transmission rate among sheep. A flock of 50 sheep was monitored for serum antibody titres against N. caninum and seroconversion over a period of six months using an indirect ELISA technique. The offspring of the herd was also investigated regarding anti-N. caninum antibodies to determine the vertical transmission rate through the indirect immunofluorescence technique. The initial and final prevalences of infection by N. caninum were 26.0% (13/50) and 72.0% (36/50), respectively, and the incidence of infection by N. caninum in the present study was 62.2% (23/37). The vertical transmission rate found was 15.4% (2/13). A high incidence of infection by N. caninum in sheep was observed, and this is the first report assessing the incidence of N. caninum among naturally infected sheep.     

Confirmed clinical Neospora caninum infection in a boxer puppy from Argentina

Generalized neosporosis was diagnosed in a 2-month-old boxer puppy. The dog had a history of progressive paralysis and muscle atrophy, followed by cervical weakness, stiff jaws and dysphagia. The dog had a 1:12,800 antibody titer for Neospora caninum and was negative for antibodies to Toxoplasma gondii by the indirect fluorescent antibody test (IFAT). After euthanasia a complete necropsy was carried out. The puppy had a megaesophagus. Microscopically, tachyzoites and tissue cysts were observed in histologic brain sections. Severe myositis was observed in esophagus and striated muscle sections and several groups of tachyzoites were associated with these lesions. Immunohistochemically, parasites in the brain and striated muscle reacted to anti-N. caninum antiserum. Western blot analysis allowed the identification of three major and four minor antigens of N. caninum tachyzoites corresponding to 30, 37, 45-kDa and 28, 29, 43, 47 and 67-kDa bands, respectively. Cerebral homogenate of the dog was inoculated into four Mongolian gerbils (Meriones unguiculatus). Forty-nine days after inoculation, all the gerbils had positive IFAT titers to N. caninum (1:200, 1:400, 1:100 and 1:400). Genomic DNA was isolated from the brain, lung and striated muscle from the puppy and from the brain of one of the inoculated gerbils. The N. caninum specific primer pair Np 6/21 produced 328 bp amplicons on electrophoretic gels. This is the first confirmed clinical case of generalized canine neosporosis in Argentina.     

Congenital Neospora caninum infection in a calf with spinal cord anomaly

Neospora caninum was identified in a calf with spinal cord anomaly in Australia. The calf was full-term and born dead. The caudal cervical and cranial thoracic segments of the spinal cord of the calf were asymmetric because of marked unilateral reduction of ventral gray matter and focal cavitation. Mild focal disseminated nonsuppurative encephalomyelitis was associated with N caninum tissue cysts. Tissue cysts were 16 to 35 microns X 10 to 27 microns, and the cyst walls were 1 to 3 microns thick. In an immunohistochemical test, the parasite stained with N caninum serum but not T gondii serum.     

A long-term study of Neospora caninum infection in a Swedish dairy herd

A longitudinal study was performed in a Swedish dairy herd where Neospora caninum had been isolated from a stillborn calf. Starting in autumn 1994, blood samples from all female animals in the herd were collected once yearly until 1999. The sera were analysed for presence of IgG1 antibodies to N. caninum by the iscom ELISA, and by an avidity ELISA to establish the timing of infection. In addition, data on reproductive performance were compiled. During the study the percentage of seropositive female animals increased from 63% to 87%. In 1994 a large number of young animals tested seropositive although their dams were seronegative, indicating that a transmission of the parasite other than the vertical had recently occurred. Low avidity values supported this assumption. The annual abortion rate increased from a mean of 2% before the initiation of the study to 9% in 1994-1998. During the same time, as judged by the avidity data, a large proportion of the animals shifted from being recently to being chronically infected. The source of the external infection in the herd could not be identified.     

用重组蛋白NcSAG1t作为ELISA诊断抗原进行土种藏系羊Neospora caninum的血清学诊断

Neospora caninum是原生动物顶器门一种原生动物性寄生虫,它最早是在一条发生瘫痪的狗上被确诊的.直到1988年,人们一直错误的把N.caninum当作Toxoplasma gondii,因为这两个寄生虫在形态学上是极为相似的.认为N.caninum是引起胎儿流产和新生犊牛死亡以及狗的神经肌肉麻痹症的主要原因.就现在掌握的资料,狗是惟一的能够排泄N.caninum卵囊的终末宿主.     

Outbreak of abortion associated with Neospora caninum infection in a beef herd

Abortion outbreaks caused by infection with Neospora caninum in beef cattle have not been well documented. Neospora caninum infection was confirmed in 4 fetuses that were aborted by cattle in a 350-head beef herd; an additional 58 cattle aborted during the next 2.5 months. Overall, 44.4% (157/354) of the cattle in the herd did not become pregnant or experienced fetal loss during this period. Initially, 81.3% (282/347) of the herd was seropositive for antibodies to N caninum, and seropositive cows were 6.2 times as likely to not be pregnant as were seronegative cows. Other potential causes of abortion were not identified in this herd. Following the outbreak, few cattle in the herd or in a second exposed herd seroconverted, but high antibody titers persisted in most seropositive cattle through the end of the calving season. Evidence of cow-to-fetus transmission of the organism was detected in > 82% of seropositive cows.     

细胞因子在犬新孢子虫感染中的作用

犬新孢子虫是一种专一性细胞内寄生虫，它的感染导致了宿主Th细胞的分化。一方面，刺激宿主产生Th1型细胞因子反应，这些细胞因子包括IL-12、IFN-7和INF-α。Th1型细胞因子反应同时还激活了产生氧自由基（FOR）、一氧化氮（NO）及其代谢物，这些细胞因子对犬新孢子虫均具有致命的杀伤力。另一方面，引发宿主产生IL-4、IL-5和IL-10等Th2型细胞因子，Th2型细胞因子主要在宿主妊娠过程中发挥作用。