Pathogens

 Toxoplasma gondii

Approximately 60 million people in the USA are infected with Toxoplasma gondii, a Class B Biodefense pathogen and an NIAID Emerging/Re-emerging Pathogen that is a major cause of food borne mortality. With one million new infections each year that result in approximately 20,000 cases of retinal infection and 750 deaths, T. gondii remains a major food borne pathogen and the second most common cause of deaths related to food-borne diseases in the United States. Indeed, the USDA has estimated an economic burden of 3.3 billion US dollars annually. Furthermore, this organism is also relevant to human health due to congenital transmission and is the cause of toxoplasmic encephalitis in immunocompromised individuals. Congenital transmission of T. gondii can have dramatic effects on fetal and neonatal health, as it can cause ocular disease, abortion, premature birth, microcephaly, mental retardation, hydrocephaly and seizures. Current studies estimate that there are 1.5 cases of congenital toxoplasmosis per 1000 births, and in the USA between 500 and 5000 infants are estimated to be infected annually. Felids (Cats) are the definitive hosts of this parasite and represent the most important stage in the life cycle of T. gondii. It is in cats where this parasite completes its life cycle and sexually reproduces in the gut. Shortly after infection, cats start to shed hundreds of millions of environmentally resistant oocysts, which are a major cause of T. gondii infections in humans and livestock. Cats themselves become infected with T. gondii by the oral uptake of oocysts or eating infected tissues from intermediate hosts. In addition to affecting human health, T. gondii also represents a significant burden for pets, wildlife and livestock, where it is widespread and can cause heavy economic losses. 

Neospora caninum 

A close relative to Toxoplasma, Neospora, is a common cause for abortion in cattle Neosporosis is one of the most important causes of abortion in cattle in America, reported incidence rates range from 7-35% throughout the United States. Moreover, neosporosis results in an estimated annual financial loss of $546.3 million and $111 million in the dairy and beef industriy, respectively. Neospora caninum, the causative agent of neosporosis, is a protozoan parasite which can infect a wide range of hosts but primarily causes disease in cattle and dogs. In addition, there has been a concern about the zoonotic potential of N. caninum. Dogs and related canids represent the definitive host of N. caninum, once infected they shed and distribute the environmentally resistant stage of this parasite, the oocyst, through their feces. Cattle are infected mainly by two routes: I. by ingestion of oocysts found in the environment, or II. transplacental transmission from the infected mother to the fetus. Once ingested, N. caninum crosses the intestinal barrier and disseminates through the host, thereby reaching the placenta causing abortions. The transplacental transmission of this parasite is highly efficient and ranges as high as 75–100%. There are no approved treatments for neosporosis in cattle to date, as the only marketed vaccine, NeoguardTM, has been removed due to ambiguous efficacy. Currently, there is neither a vaccine nor a drug commercially available for the prevention of bovine neosporosis. Farmers with infected animals are left with only two options, either they allow infected animals to live and likely spread the disease or cull N. caninum-infected cattle from the herd.