PowerPoint Presentation Food borne Pathogens Module 12 Eukaryotic Parasites Eukaryotic parasites Several different parasites can cause infestations and associated disease in humans and animals via a f.
Food-borne Pathogens Module 12 Eukaryotic Parasites Eukaryotic parasites Several different parasites can cause infestations and associated disease in humans and animals via a food route (or faecal/oral route) Most are acquired due to contamination of crops and by consuming improperly cooked meat of animals infected with parasites and sometimes due to lack of hygiene by food handlers The main sources of contamination by parasites include: Use of manure as fertiliser for crops Manure may contain eggs/cysts of the parasites Livestock infected by parasites are left to graze near crops They may shed eggs/cysts of parasites onto ground and potentially contaminate crops Wild animals/birds may spread parasite eggs/cysts onto crops Irrigation water is contaminated by manure or sewage Aerosols from spraying contaminated water or slurries The main sources of contamination by parasites include: Poor hygiene practices by food handlers Washing food products that are consumed raw with contaminated water Using contaminated water to make ice and frozen/chilled foods Using contaminated water for making food that receives only minimal processing Entamoeba Cryptosporidium tapeworms Trichinella spiralis Entamoeba Toxoplasma gondii Ascaris Major foodborne parasites as designated by the FAO (United Nations) Parasite Type Food type Taenia spp tapeworms meat Echinococcus spp (E granulosus, E multilocularis) tapeworms fresh produce Trichinella spiralis Nematode (pork worm) pork Opisthorchiidae flatworms freshwater fish Ascaris spp Nematode (hook work fresh produce or round worm) Cryptosporidium spp protozoan fresh produce, fruit juice, milk Entamoeba histolytica protozoan fresh produce Toxoplasma gondii protozoan meat (except birds), vegetables Giardia duodenalis protozoan fresh produce Cyclospora cayetanensis protozoan fresh produce Naegleria fowleri Protozoan Various (very rare) Foodborne tapeworms (cestodes) Taenia Head (scolex) of Taenia Rostellum (showing hooks) Causes taeniasis Parasitic infection acquired by consuming eggs or proglottid (egg packet) of the tapeworm Three major species - Taenia saginata – beef tapeworm - Taenia solium – pork tapeworm - Taenia asiatica suckers Parasitism in humans mainly occurs in areas where beef and/or pork are eaten raw or very lightly cooked Mostly Latin America, Eastern Europe, Russia, subSaharan Africa, some parts of Asia Infestation causes digestive problems: abdominal pain, loss of appetite, weight loss, upset stomach, shed parts of tapeworm, eggs and proglottids in faeces Cysticercosis Taenia solium can cause a more serious illness called cysticercosis This disease is acquired by eating food contaminated by Taenia solium eggs that come from a person (usually a food handler) who has Taenia solium infestation Cannot get this form of parasitism directly from meat (pork) Infestation spreads to the skin, brain, eyes and muscles where the tapeworm forms cysts, which become calcified (cysticerci) - Leads to swelling, atrophy, fibrosis of muscles - Eye damage with possible vision loss - Nodules in the skin that can be painful to touch - Brain damage leading to seizures, frequent headaches About 1200 people die each year (worldwide) Treatment - anti-helminthic drugs, other drugs to treat symptoms, surgery to remove cysts (e.g eyes) Taenia solium lifecycle The acquisition of the tapeworm is enhanced due to consumption of human faecal contaminated crops and consumption of meat from infested undercooked pork Echinococcus spp Tapeworm (cestode) genus that causes a hyatid disease called echinococcosis Echinococcosis comes in two forms: Cystic echinococcosis – obtained from ingesting eggs of Echinococcus granulosus, associated mainly with canines (the definitive host), livestock (intermediate hosts) The tapeworm forms slowly cysts in the liver, lungs and other organs such as the bone, heart, brain, eyes Rupture of cysts may cause death of the host due to anaphylactic shock Alveolar echinococcosis - obtained from ingesting eggs of Echinococcus multilocularis, associated mainly with canine species (the definitive host), rodents (intermediate hosts) The tapeworm causes the development of tumour-like formations in various organs including liver, lungs, and brain Lack of treatment always results in death Treatment: requires chemotherapy and surgical removal of cysts Echinococcus granulosus life cycle and parasitism Possible connection between Toxoplasma, gut microbiome and neurological symptoms Cause and effect relationships under active research healthy schizophrenic, depressive It has been shown recently drugs, such as arctigenin, that interfere with the proinflammatory cascade that occurs during a T gondii infection cycle can relieve depressive symptoms Arctigenin – a lignan derived from plants (greater burdock, snow lotus etc.) Cheng et al 2020 Int Immunopharmacol Entamoeba histolytica (and E dispar) • Anaerobic parasitic amoeba that causes infections in humans and transiently in animals called amoebiasis or amoebic dysentery Humans are the natural host of this parasite dwelling in the intestine Its genome is 21 megabases in size, is AT-rich (25% G+C) and contains many novel receptor proteins that allows interaction with the human host Codes around 7500 proteins • Foodborne infections associated with Entamoeba involve ingestion of contaminated food (or water) containing cysts of the parasites • The cysts are shed in the faeces of individuals parasitised by the amoeba Approximately 90 million people have amoebiasis worldwide at any one time mostly in tropical zone developing nations/regions Annual death toll is about 100000 people Entamoeba histolytica (and E dispar) amoebiasis Symptoms • Amoebiasis causes disease that varies ranging from abdominal pain, mild diarrhea to severe bloody diarrhea (termed amoebic dysentery) and fever • In some people Entamoeba can invade the body via ruptured capillaries with the trophozoites travelling thorough the body forming abscesses, especially in the liver and lungs This is called fulminant amoebiasis Without treatment it is always fatal Treatment Several antibiotics can aid in suppressing amoebiasis, mostly metronidazole or tinidazole are used metronidazole tinidazole Entamoeba histolytica life cycle and infection via via trophozoites which also can become invasive that leads to brain and liver infection in the fulminating version of amoebiasis (~0.7% of cases) Most cases are “self-limiting” and asymptomatic so many people probably are infected without realising it Naegleria fowleri An amoebic flagellate parasite that causes devastating brain infections in humans - called primary amoebic meningoencephalitis – almost 100% fatality N fowleri is mildly thermotolerant and can be found in water bodies including some hot springs and warm bathing pools N fowleri initiates infections due to aspiration of trophozoites into the nasal passage typically this is water but theoretically could also include food (or aerosols derived from food) Fortunately this is very rare The N fowleri trophozoite can form cysts though only when under stress (low temperature usually) and does not forms cysts in hosts This spread of the parasite only involves the trophozoite form N fowleri invades the central nervous system It can move through the cerebrospinal fluid in its flagellate form It invades the brain via the nerve cells that line the nasal cavity cyst trophozoite flagellate Naegleria fowleri may be able to initiate infection via food if trophozoites are aspirated during drinking or consumption of contaminated food or water Primary amoebic meningoencephalitis • This is the disease caused by N fowleri It affects the brain and has >95% fatality Those who survive are often disabled for life • The N fowleri preferentially moves to the brain via the olfactory nerves thus first symptoms (3-7 days) is loss of the ability to smell (and subsequently taste) • Symptoms worsen progressing from constant headache, to nausea, rigidity of the neck, then vomiting, delirium, seizures and then coma • The parasite rapidly spreads eventually destroying nerve cells in the medulla oblongata region of the brain responsible for autonomic functions This results in death from respiratory failure Genome of N fowleri is about 28 megabases and codes around 14000 proteins Treatment No effective treatments are available If condition is diagnosed rapidly enough certain drugs may stop the infection Vaccine development is underway Giardiasis Gardiasis is a disease caused by the anaerobic obligately parasitic species Giardia duodenalis (which now includes G intestinalis , G lamblia) Giardia occurs world-wide in humans, animals (both domestic and wild) including reptiles and birds Humans are the primary host Most exposure to parasites is due to ingestion of cysts via water Foodborne route occurs due to preparation of foods with contaminated water Cysts are quite hardy and survive in cold water (months), and freezing Cysts are killed when dried or exposed to the sun Giardia is mainly found in water bodies in warm climates Cells have characteristic appearance Dark spots are nucleus Regions Genome is only about 11.5 megabases (5 chromosomes) and has half the number of proteins as T gondii Giardiasis Prevalence and Morbidity Typically around 2% prevalence but up to 15% in developing nations Most common in young children (toddlers 1-4 years old) and those of middle age (40-44 years old) Giardiasis illness is generally self-limiting but immunocompromised individuals can develop chronic disease leading to reduced lifespan Giardiasis in the USA by age Transmission of Giardia • Giardia cysts can be directly transmitted to new hosts in contaminated water and/or food • Ingested cysts release trophozoites which multiply and encyst (form cysts) in the intestine • Cysts are then shed in faeces cyst Prevention of Giardiasis trophozoite Do not drink contaminated water or water from untreated lakes, rivers, wells Boil the water or filter the water – pore size µm or less Water supply should be chlorinated (chlorine kills Giardia) Always wash raw fruits and vegetables with potable water Giardia duodenalis transmission to humans via cysts Giardiasis - disease • Disease incubation period: 1-25 days • Most infections are asymptomatic • Symptoms of clinical disease: mild to severe gastroenteritis – diarrhea, abdominal pain/cramps, bloating, nausea, fatigue, weight loss • Infections last