Neospora caninum is a coccidian parasite that was identified as a species in 1988. Prior to this, it was misclassified as Toxoplasma gondii due to structural similarities. The genome sequence of Neospora caninum has been determined by the Wellcome Trust Sanger Institute and the University of Liverpool. Neospora caninum is an important cause of spontaneous abortion in infected livestock.
Life cycle and transmission
Neospora caninum has a heteroxenous life cycle, with the sexually reproductive stage occurring in the intestine of a definitive host. Until recently, the only known definitive host was the domestic dog. New research has determined that coyotes (Canis latrans), gray wolves (Canis lupus), and Australian dingos (Canis lupus dingo) are also definitive hosts. Oocysts passed in the feces of the definitive host are ingested by an intermediate host, such as cattle. These become permanently infected, and form tissue cysts. Pregnancy activates these cysts, and active infection often causes spontaneous abortion. If the aborted foetus and membranes are then eaten by the definitive host, they cause further infection and the cycle is complete. Transplacental transmission (passage from mother to offspring during pregnancy) has also been shown to occur in dogs, cats, sheep and cattle. Other carnivores, for example the red fox (Vulpes vulpes), may also be intermediate hosts, but they are not known to be definitive hosts. Neospora caninum does not appear to be infectious to humans. In dogs, Neospora caninum can cause neurological signs, especially in congenitally infected puppies, where it can form cysts in the central nervous system.
The discovery that coyotes are definitive hosts may increase the risk of transmission of N. caninum to domestic livestock as well as to wild ruminants such as white tailed deer (Odocoileus virginianus). Coyote range now includes most of North and Central America. Studies suggest that the parasite may be widespread among wildlife and that infection cycles cross over between wild and domestic animals.
Recent studies have broadened the list of known intermediate hosts to include birds. N. caninum has recently been found to infect domestic chickens and house sparrows (Passer domesticus) which may become infected after ingesting parasite oocysts from the soil. Sparrows, which are common in urban and rural areas, may serve as a food source for wild and domestic carnivores. N. caninum has also been detected in common buzzards (Buteo buteo) and magpies. The presence of birds in cattle pastures has been correlated to higher infection rates in cattle. Birds may be an important link in the transmission of N. caninum to other animals.
Treatment and control
In addition to being an important cause of cattle abortions, neosporosis is a significant disease in dogs throughout the world. If the disease is caught early, dogs may be successfully treated with clindamycin and other antiprotozoan drugs. However, the disease is often fatal to young puppies. Preventative vaccines have been tested on cattle. An inactivated vaccine was made commercially available but had mixed results. A live vaccine using attenuated N. caninum tachyzoites has been more successful but is expensive to produce. Other treatment options aim at prevention of the disease. Prevention requires an understanding of the transmission cycle, especially the connection between cattle and dogs (canids). Canids may pick up the parasite from eating infected material and spread the disease through contaminated feces. One control method is to test for the disease and remove infected cattle from the herd. Another method of control is preventing canids from entering the cattle holding area.
- Dubey JP (Oct 1999). "Neosporosis—the first decade of research". Int J Parasitol. 29 (10): 1485–8. doi:10.1016/S0020-7519(99)00134-4. PMID 10608433. http://linkinghub.elsevier.com/retrieve/pii/S0020-7519(99)00134-4.
- Reid AJ, Vermont SJ, Cotton JA, Harris D, Hill-Cawthorne GA, Konen-Waisman S, Latham SM, Mourier T, Norton R, Quail MA, Sanders M, Shanmugam D, Sohal A,Wasmuth JD, Brunk B, Grigg ME, Howard JC, Parkinson J, Roos DS, Trees AJ, Berriman M, Pain A, Wastling JM (2012). "Comparative Genomics of the Apicomplexan Parasites Toxoplasma gondii and Neospora caninum: Coccidia Differing in Host Range and Transmission Strategy". PLoS Pathogens 8 (3): e1002567. doi:10.1371/journal.ppat.1002567. PMID 22457617. http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1002567.
- McAllister MM, Dubey JP, Lindsay DS, Jolley WR, Wills RA, McGuire AM (Sep 1998). "Dogs are definitive hosts of Neospora caninum". Int J Parasitol. 28 (9): 1473–8. doi:10.1016/S0020-7519(98)00138-6. PMID 9770635. http://linkinghub.elsevier.com/retrieve/pii/S0020751998001386.
- Dubey, JP; MC Jenkins, C Rajendran, K Miska, LR Ferreira, J Martins, OCH Kwok, S Choudhary (September 2011). "Gray Wolf (Canis lupus) is a natural definitive host for Neospora caninum". Veterinary Parasitology 181 (2-4): 382–387. doi:10.1016/j.vetpar.2011.05.018. http://www.sciencedirect.com/science/article/pii/S0304401711003566. Retrieved 20 February 2012.
- Gondim, LFP; MM McAllister, WC Pitt, DE Zemlicka (February 2004). "Coyotes (Canis latrans) are definitive hosts of Neospora caniinum.". International Journal for Parasitology 34 (2): 159–161. doi:10.1016/j.ijpara.2004.01.001. http://www.sciencedirect.com/science/article/pii/S0020751904000025. Retrieved 20 February 2012.
- King, JS; Slapeta J, Jenkins DJ, Al-Qassab SE, Ellis JT, Windsor PA (July 2010). "Australian dingoes are definitive hosts of Neospora caninum". International Journal of Parasitology 40 (8): 945–950. doi:10.1016/j.ijpara.2010.01.008. PMID 20149793.
- Almería S, Ferrer D, Pabón M, Castellà J, Mañas S (Aug 2002). "Red foxes (Vulpes vulpes) are a natural intermediate host of Neospora caninum". Vet Parasitol. 107 (4): 287–94. doi:10.1016/S0304-4017(02)00162-0. PMID 12163240. http://linkinghub.elsevier.com/retrieve/pii/S0304401702001620.
- Barber JS, Payne-Johnson CE, Trees AJ (Dec 1996). "Distribution of Neospora caninum within the central nervous system and other tissues of six dogs with clinical neosporosis". J Small Anim Pract 37 (12): 568–74. doi:10.1111/j.1748-5827.1996.tb02332.x. PMID 8981277.
- Gondim, LFP; McAllister MM, Mateus-Pinilla NE, Pitt WC, Mech LD, Nelson ME (December 2004). "Transmission of Neospora caninum between Wild and Domestic Animals". The Journal of Parasitology 90 (6): 1361–1365. http://ddr.nal.usda.gov/bitstream/10113/20958/1/IND43682384.pdf. Retrieved April 4, 2012.
- Darwich, L; Cabezón O, Echeverria I, Pabón M, Marco I, Molina-López R, Alarcia-Alejos O, López-Gatius F, Lavín S, Almería S (February 2012). "Presence of Toxoplasma gondii and Neospora caninum DNA in the brain of wild birds.". Veterinary Parasitology 183 (3-4): 377–381. doi:10.1016/j.vetpar.2011.07.024. http://www.sciencedirect.com/science/article/pii/S0304401711004936.
- Gondim, Leane S. Q.; Kiyoko Abe-Sandes, Rosângela S. Uzêda, Mariana S.A. Silva, Sara L. Santos, Rinaldo A. Mota, Sineide M.O., Vilela, Luis F.P. Gondim (February 2010). "Toxoplasma gondii and Neospora caninum in sparrows (Passer domesticus) in the Northeast of Brazil". Veterinary Parasitology 168 (1-2): 121–124. doi:10.1016/j.vetpar.2009.09.055. http://www.sciencedirect.com/science/article/pii/S0304401709006232. Retrieved March 3, 2012.
- Mineo, T.W.P.; A.O.T. Carrasco, T. F. Raso, K. Werther, A.A. Pinto, R.Z. Machado (December 2011). "Survey for natural Neospora caninum infection in wild and captive birds". Veterinary Parasitology 182 (2-4): 352–355. doi:10.1016/j.vetpar.2011.05.022. http://www.sciencedirect.com/science/article/pii/S030440171100375X.
- Dubey, J.P.; Dorough, K.R., Jenkins, M.C., Liddell, S., Speer, C.A., Kwok, O.C.H., Shen, S.K. (August 1998). "Canine neosporosis: clinical signs, diagnosis, treatment and isolation of Neospora caninum in mice and cell culture". International Journal for Parasitology 28 (8): 1293–1304.
- Andrianarivo, AG; Rowe, JD, Barr, BC, Anderson, ML, Packham, AE, Sverlow, KW, Choromanski, L, Loui, C, Grace, A, Conrad, PA (August 2000). "A POLYGEN-adjuvanted killed Neospora caninum tachyzoite preparation failed to prevent foetal infection in pregnant cattle following i.v./i.m. experimental tachyzoite challenge". International Journal for Parasitology 30 (9): 985–990. doi:10.1016/S0020-7519(00)00088-6. http://www.sciencedirect.com/science/article/pii/S0020751900000886.
- Romero, JJ; Pérez, E, Frankena, K. (September 2004). "Effect of a killed whole Neosporacaninum tachyzoite vaccine on the crude abortion rate of Costa Rican dairy cows under field conditions". Veterinary Parasitology 123 (3-4): 149–159. doi:10.1016/j.vetpar.2004.06.016. http://www.sciencedirect.com/science/article/pii/S0304401704002742.
- Reichel, MP; Ellis, JT (September 2009). "Neospora caninum – How close are we to development of an efficacious vaccine that prevents abortion in cattle?". International Journal for Parasitology 39 (11): 1173–1187. doi:10.1016/j.ijpara.2009.05.007. http://www.sciencedirect.com./science/article/pii/S0020751909002203. Retrieved April 13, 2012.