Biology and Control of Giardia and Cryptosporidium Miodrag Belosevic, PhD, FRS(TMH), Department of Biological Sciences University of Alberta

Waterborne Protozoa  Cryptosporidium  Giardia  Entamoeba  Naegleria  Toxoplasma  Acanthamoeba

The Course of Protozoan Infections in Different Hosts Latent Period Acute Phase Elimination Phase

Characteristics of Infection  low numbers of parasites required to initiate infection  multiplication in the host- transmission  self-limiting - except immundeficient individuals  Zoonosis - cross-species transmission

Cryptosporidium: Public Health Significance  Worldwide prevalence about 10%  Zoonosis, human and animal genotypes  Oocysts ubiquitous in surface waters  Difficult to remove, and hard to kill  Drinking water - amplifier for disease  Up to 20% of general population may be considered at higher risk

Cryptosporidiosis: The Disease  Serious disease in the young, pregnant women, patients undergoing chemotherapy and elderly  Potentially fatal in immundeficient hosts  Infectious dose in healthy humans is low: ID 50 about 130 oocysts  No effective chemotherapy available

Giardia: The Organism  obligate intestinal parasites of all classes of vertebrates  more than 100 described species  two stages in the life cycle: the motile trophozoites that inhabit the small intestine of the host, and the resistant cysts found in the environment

Giardiasis: Public Health Significance  Worldwide prevalence about 8%, much higher in endemic areas  Zoonosis  Most prevalent in day care centers, mental institutions, male homosexuals  Children, elderly and immunodeficient persons more susceptible  Transmitted by direct contact, food or water  Chemotherapy available- some drug resistance

Giardiasis: The Disease  asymptomatic: largest group  symptomatic: self-limiting infection, diarrhea, abdominal cramps,fever, nausea and weight loss  symptomatic: chronic infection, immunodeficient individuals, malabsorption, food intolerance, chronic inflammation of the mucosa

Parasites in Water Detection in Environment Inactivation Efficacy Viability Assays Animal Infectivity

Measures of Viability  ANIMAL INFECTIVITY: expensive, very reliable  EXCYSTATION: not accurate- overestimates viability  CELL CULTURE: underestimates viability, contamination  NUCLEIC ACID DYES: inexpensive, convenient & rapid

Animal Infectivity  Answers the public health question: will the organism cause an infection?  Depends on the dose-response in susceptible animal hosts  Complex, labor intensive, time- consuming

Infectivity Assay Infectivity in neonatal CD-1 mice Flow cytometry of lower half of intestine

 Organisms are organic particles  Sources in water supplies include:  human wastes from point-sources  uncontrolled non-point source pollution from agriculture and natural sources  disposal/recycling of water treatment wastes  View microbial reduction as a system of multiple processes designed to eliminate/inactivate infectious particles Modern Concept of Inactivation

Control of Protozoa In Drinking Water  Multiple barrier approach: –Filtration –Chemical inactivation- ozone, combination of disinfectants –Medium-pressure ultraviolet light (UV)  Monitoring: –Presence of protozoa in raw water –Viability assessment in finished water

 Water quality  dissolved organic carbon  pH  temperature  turbidity  Concentration of oxidant  Contact time Factors Affecting Chemical Inactivation

From: C.N. Haas et al Journal of the American Water Works Association, 88(9): Overall oocyst treatment Influent oocysts (no./100 L) Inadequate protection Adequate protection Degree of Microbial Inactivation Required for 1:10,000 Annual Risk /Person

 Health effects criteria:  serum antibody surveys of communities  parasitological survey of communities  Quantitative risk assessment:  concentration of parasite in source water  assume annual per person risk level of 1:10,000 Microbial Reduction Goals