Toxoplasma gondii: the world s most successful parasite?

Toxoplasma gondii: a one health approach Over 100 Years since the discovery of Toxoplasma: (Nicolle and Manceaux, 1908 in Tunisia and Splendore, 1908 in Brazil) Huge impact across the world: medical, veterinary, environmental health Excellent model organism to study cell biology of apicomplexan pathogens Toxoplasma can infect all warm blooded animals and there is only one species that will infect all hosts Toxoplasma can be grown in many cell lines in vitro, amenable to genetic manipulation How can we work better together to tackle Toxoplasma globally?

Toxoplasma gondii: a one health approach Biology and Life cycle Transmission Impact Host parasite interactions Prevention and control strategies

Toxoplasma gondii

Toxoplasma gondii: Impact Major cause of abortion in sheep and goats worldwide Cause of 24% of ovine abortions in UK Recent reports from Brazil of T. gondii in sheep and goat foetuses (Pescador et al 2007, de Moraes et al 2011) Congenital infection in women Eye disease, brain damage, life long learning disabilities UK : 5 per 100 000 births Brazil: 1 per 1000 births (35% neurological disease, 80% eye disease, 40% hearing loss) Immuno-compromised people Cancer patients, Transplant patients Immunocompetent people Eye disease in congenitally infected children in Brazil is significantly more severe than in European children (Gilbert et al 2008)

Toxoplasma gondii: sheep Survey of 125 flocks across Scotland : sero-prevalence 52%

Toxoplasma gondii: Sheep transmission

Toxoplasma gondii: Sheep Disease Major cause of abortion in sheep in many countries worldwide Caused by a protozoan parasite Toxoplasma gondii Abortion can occur following a primary infection in pregnancy Stage of gestation when infection occurs is critical to the clinical outcome, infection early in pregnancy causes more severe disease Following infection, sheep develop good immunity which will protect against disease in a subsequent pregnancy

Ovine T. gondii: Immune responses Monitor in real time immune responses induced in sheep following primary and secondary infections with T.gondii Key protective immune responses Innate immunity CD4+ T-cells CD8+ T-cells IFNγ Animals recovering from primary infection are immune to secondary challenge

Toxoplasma gondii: Toxovax vaccine S48 incomplete strain Originally isolated in New Zealand Induces protective immunity against ovine toxoplasmosis Vaccinated + challenged: 80% viable lambs Control + challenged: 10% viable lambs Control not challenged: 90% viable lambs Immunity duration 18 months Live vaccine Shelf life; safety Only commercial vaccine available worldwide against toxoplasmosis

Toxoplasma gondii: prevalence Blood donors in Scotland (3700 samples) Seroprevalence of 12 % MRC sudden death brain bank % 200 cases. Molecular detection hind brain. Prevalence of 18%. (Burrells et al 2016) In Brazil, up to 50% of elementary school children and 60 % of women of child bearing age have antibodies to T. gondii (Dubey, Lago, Gennari et al 2012) What is the major route of transmission to people? Risk factor analysis 60% of cases related to consumption of undercooked meat containing T. gondii tissue cysts (Cooke et al 2000)

Toxoplasma gondii: transmission Consumption of oocysts contaminating feed, water, pasture Consumption of undercooked meat containing T. gondii cysts Vertical transmission from mother to foetus

Toxoplasma gondii: Food borne pathogen Disease burden foodborne pathogens Netherlands, Havelaar (2009) WHO Global Burden Foodborne pathogens (2015)

EFSA: Detection of T.gondii in food animals 7 European countries involved, 38 participants, 12 organisations Cattle, sheep, pigs, chickens horses Harmonise methodology to detect T. gondii (serology/molecular) Can we relate seroprevalence with presence of T.gondii in meat?

EFSA: Detection of T.gondii in food animals Probability of detecting T. gondii in seropositive animals (Opsteegh et al 2016) Pigs Sheep and Goats Chickens Cattle Horses Husbandry practice Consumer preferences Quantitative Risk assessment Experimental infection of cattle (Burrells et al 2018)

Safer meat for human consumption: vaccination of pigs to reduce T.gondii cysts 4 weeks post vaccination Cull 6 wks Mouse bioassay Pathology immunology Molecular detection

Safer meat for human consumption: vaccination of pigs to reduce T.gondii cysts Detection of T.gondii in tissues using mouse bioassay Brain Diaphragm Heart Chop Loin Forelimb Massater Tongue

Safer meat for human consumption: vaccination of pigs to reduce T. gondii cysts Vaccination of pigs with live S48 attenuated strain tachyzoites gave significant protection against T. gondii cysts in tissues Detection using PCR and mouse bioassay In experimentally challenged animals both oocysts and cysts resulted in widespread dissemination of T. gondii to different tissues Similar results have been achieved by vaccination of lambs to reduce T. gondii cysts in meat. Burrells et al 2015 Katzer et al 2014

T. gondii: Safer meat for human consumption a one heath approach High Risk meat products: Raw products eg: steak tartare Undercooked products eg: lamb chop, venison Meat from outdoor reared animals, those with higher prevalence Interventions: Biosecurity on farms Vaccination? Freezing meat Cooking meat Curing, salting Cost-benefit analysis of preventative intervention. Freezing meat and Biosecurity on farms. (Suijkerbuijk et al 2018)

Toxoplasma gondii: Food and water borne pathogen

Toxoplasma gondii: water borne pathogen T. gondii oocysts can survive for long periods of time in water several months to years. Waterborne outbreaks of toxoplasmosis in people linked to oocyst contamination of drinking water Canada (Bowie et al 1997) Brazil, Parana(Daufenbach et al 2002; de Moura et al 2006) Outbreak was linked to a cistern that supplied public water T. gondii isolates from cats associated with the cistern and in the water were epidemiologically linked to people clinically affected based on peptide typing of sera. 426 people affected; congenital toxoplasmosis, eye disease, enlarged lymph nodes

T. gondii in water samples in Scotland Scottish water public water supplies 147 different locations across Scotland 45 locations were positive for T. gondii (Filtration, DNA extraction, qpcr 529bp, sequencing).wells et al 2015 Linked to rainfall in Autumn

Toxoplasma gondii prevention and control: A one health approach Vaccination: livestock, cats, people? Vaccine target, live or dead? Genetics, Biology, Immunology (Innes et al 2011; Garcia et al) Biosecurity: livestock farms Diagnostics and detection: risk from contaminated food and water; screening programmes, parasite strain variation and virulence Treatments: cost benefit analysis, efficacy Consumer practices: heating, freezing, salting, irradiation, water filter treatments