2 - Food microbiology and disease

• Showing an awareness of the balance of health versus disease in populations is a key aspect of public health.
• Types of water borne disease are discussed.
• Norovirus, Cryptosporidium, and other organisms are examples of water-borne diseases.
• Clean water contains mainly particulates that could easily be filtered out and water becomes safe, as long as no pathogens.
• Clear water could still be full of microorganisms, not sterile.
• Accessibility to clean/safe water is a crucial aspect of microbiology.
• Surface water is unsafe for drinking due to its untreated nature.
• 785 million people globally do not have access to safe drinking water within 30mins of their home.
• 2 billion people are drinking not safe water, including 1.8 billion from faecally contaminated water sources.
• 842 000 deaths yr -1 are attributable to unsafe water supply, inadequate sanitation and lack of hygiene.
• 71% of the global population use a safely managed drinking water service.
• 90% of the global population use at least a basic drinking water service.
• WHO states that no child should die or get sick as a result of drinking contaminated drinking water, being exposed to other people’s excreta, or having no place to wash their hands.
• No child should have to stay away from school for lack of a clean toilet and privacy.
• No one should have to suffer the indignity of having to defecate in the open.
• In the UK, water used to flush into toilets is clean.
• E. coli 0157:H7 (Disease: gastroenteritis) is a viral disease caused by Norovirus (Symptoms: Diarrhoea and vomiting) and Rotovirus (Symptoms: Diarrhoea and vomiting).
• Norovirus (Family: Caliciviridae, Genus: Norovirus) is a shape-shifter virus that can cause outbreaks in closed communities like cruise ships and nursing homes.
• Seasonality of Cryptosporidium peaks in spring and autumn months.
• Norovirus has three open reading frames: ORF1 encodes a 200kDa poly-protein that is auto-processed by a virally encoded 3C-like protease to yield non-structural replicase proteins, ORF2 encodes a structural capsid protein, 57kDa (subject to variation), and ORF3 encodes a minor structural protein, 22kDa.
• Host factors and virulence factors of Cryptosporidium include symptomatic episodes of uncontrolled diarrhoea, immune suppression, and reduced/lack of immunity.
• Plasmodium spp (P. falciparum, P. vivax, P. ovale, P. malariae) (Disease: Malaria) are protozoan diseases that cause cholera-like symptoms.
• The life cycle of Cryptosporidium involves ingestion of cysts, excystation of sporozoites, adhesion of sporozoites to gut epithelia, invasion, and multiplication and survival in the host.
• Protozoan diseases include Cryptosporidium parvum (Disease: Cryptosporidiosis) and Schistosoma spp (Disease: Schistosomiasis), the latter being transmitted via snails in freshwater.
• Age and sex distribution of Cryptosporidium is more common in young people, more common in females and males aged 25-35 due to parenting, and less frequent in the old.
• Norovirus Genotype I and II have different binding domains that allow protein entry to host cells, and different antigenic structures allowing escaping antibodies.
• Risk factors for Cryptosporidium infections include human behaviour such as unintentional defecation in swimming pools, petting zoos/farms, and age.
• Waterborne diseases include bacterial diseases like Vibrio cholerae 01 El Tor (Disease: Cholera) which cause severe loss of water and electrolytes, and are associated with sanitation issues.
• Norovirus is a “shape-shifter” virus that can cause outbreaks in closed communities like cruise ships and nursing homes.
• Outbreaks of Cryptosporidium are monitored by epidemiological studies.
• Cryptosporidium (Family: Cryptosporidiiae, Genus: Cryptosporidium) is a protozoan parasite that causes diseases like Cryptosporidium parvum; Cryptosporidium hominis.
• Norovirus and Cryptosporidium have similar modes of transmission and control measures include sanitation and hygiene.
• Norovirus is a non-enveloped, icosahedral virus with a 38nm diameter, and its genome is a 7.5 kb positive sense, single stranded RNA (Baltimore Classification IV).
• Hygiene is an important component to safe water, as it is important for food safety, hygienic practices for personal health and the health of those around you.
• Water filtration removes a lot of toxins and chemicals.
• Sand removes very small particles including bacteria and large parasites.
• Bottled water is a polisher filter that removes viruses and makes water look good.
• Mains water is monitored for microbial contamination, with limits for bacterial count, coliforms, total viable counts, and indicator organisms such as Campylobacter, Norovirus, Cryptosporidium, Enteric bacteria, and others.