3.2. Neosporosis

Neospora is a protozoan belonging to the phylum Apicomplexa, Sporozoa class, Eucoccidiida order and Sarcocystidae family [21]. Neospora caninum is a parasite coccidia, intracellular exclusively, forming cysts that causes neosporidiose, a disease that has been disseminated in the continents generating a high rate of infected cattle and dogs [22]. In the genus Neospora were identified only two species N. caninum [23] isolated from dog brain and N. hughesi [24, 25] isolated from the brain and spinal cord of horses [24]. It has not been described any cases of the disease in humans [26]. Dogs (Canis lupus familiaris) [27], coyotes (Canis latrans) [28], dingo (Canis lupus dingo) [29] and gray wolves (Canis lupus) [30] have been identified as definitive hosts of the parasite and are significant in the transmission of the parasite to other animals. The prevalence of antibodies against N. caninum in dogs is the result of research in various parts of world, which has reached from 4 to 54.2% [31, 32]; this percentage can be varying because of habitat, age, living of dogs with cattle, diet and serological technique employed etc., among others [33]. The life cycle of N. caninum has three forms: tachyzoites, bradyzoites in the cysts and sporozoites in the oocysts. However, the tachyzoites and bradyzoites are intracellular stages identified in intermediate hosts [34]. The tachyzoites are responsible for the acute phase and has the ovoid or circular shape. Bradyzoites are in latent stages, through tissue cysts that are resistant to acid solution pepsin [35].

Horizontal transmission (postnatal) is due to the ingestion of water or food contaminated with oocysts eliminated by dogs, especially in cases of abortion outbreaks. It is identified as the association between seroprevalence and abortions in bovines, when the presence of dogs could increase the incidence of the disease in both species. Dogs present in farms were identified with greater prevalence of infection than in urban area [36]. This is due to the dogs ingest infected bovine foods such as foetuses, foetal membranes and fluids [37]. In dogs, neosporidiose can develop neuromuscular, cardiac, pulmonary and skin lesions changes, there still descriptions of dermatitis, cardiomyosite and pneumonia in this species [38, 39]. Vertical transmission via lactogenic have been reported in calves experimentally and the presence of DNA of N. caninum was also observed in the colostrum of cows infected, reporting the possibility of transmission of N. caninum by colostrum [40].

Contamination can occur vertically when a bitch with subclinical infection transmits N. caninum to its foetuses and litters can be born infected [41]. The congenitally infected animals are the most severe cases; however, the infection can occur in animals of all ages. Young animals manifest hind limb paralysis that occurs at an accelerated rate, and incoordination can cause paresis of hind limbs in adult dogs [42, 43]. For a reliable diagnosis: detailed history and description, good physical examination and laboratory tests are necessary [42]. Haematological and biochemical tests are not enough to confirm the diagnosis of this disease, since the laboratory diagnosis is affected by means of serological and parasitological examinations. However, the muscle biopsy is considered important for the diagnosis of neosporidiose [23, 44]. The use of immunohistochemistry is also of paramount importance to identify tachyzoites and cysts in the tissues [37]. Analysis of the cerebrospinal fluid is another form of diagnosis that can facilitate the identification of this disease. The inflammatory cell count demonstrates an inflammatory or infectious situation and tachyzoites display may indicate protozoal encephalomyelitis, and can also identify bradyzoites in cerebrospinal fluid. In the dog faeces, the oocysts of N. caninum can be observed using the flotation technique [37, 45].

The PCR is essential to detect the DNA of the parasite in the faeces of the definitive host and thus used to confirm the diagnosis. This technique is also used to perform DNA detection in the intermediate host [46, 47]. Serological tests such as indirect immunofluorescence assay, agglutination test Neospora (NAT) and multiple tests of ELISA were made for diagnosis in dogs [48]. IFA was the initial test to identify antibodies against N. caninum. Immunofluorescence with greater than or equal to title 1:50 demonstrates dog contact with the agent. The NAT test demonstrates the agglutination of tachyzoites in the presence of specific antibodies contained in the serum, abolishing the use of secondary antibodies used in the previous tests. This test has identified specificity and similar sensitivity of the IFA [21, 49].

Macroscopic lesions caused by N. caninum is rare, however in experimental infections, it was identified necrosis of the foetal placental villi, necrosis and inflammation [50]. For the treatment of dogs clindamycin (11‐22 mg/kg, BID, TID), sulphonamides (15 mg/kg bid) and pyrimethamine (1mg/kg SID) [51] are used. However, the treatment efficiency is not effective, but there are data that demonstrate an effective response against neosporosis in the symptoms of adult dog administration associated with pyrimethamine and sulphadoxine for 1 month [52]. For the prophylaxis and control of N. caninum infection, the reproduction of positive dogs that have already demonstrated compatible symptoms or have calved infected puppies and sick should be prevented. It should also be able to prevent these carnivores eat foods such as meat or raw entrails, and especially farm animals [42]. To prevent the ingestion of aborted foetuses and placental membranes should discard these materials in an appropriate place, since we do not have efficient commercial vaccines on the market [53].
