# Food and Drinking Water as Sources of Pathogenic Protozoans: An Update
## 18 Discussion
\begin{table}
\begin{tabular}{c c} \hline
**Infectious Agent** & **Dietary Infection Sources in Cases and Outbreaks * \\ \hline _Dientamoeba fragilis_ & None reported \\ _Pentatrichomonas hominis_ & None reported \\ \hline \end{tabular}  
* Ascertained or most probable, determined by statistical association or by direct evidence in cases and outbreaks.  
\end{table} 
Table 1: _Cont._Figure 3: Schematic representation of the contamination sources at the origin of cases and outbreaks reported since 2019 for foodborne and waterborne protozoans [90,122,123,131,132,133,154,157,168–170, 172,173,200,210,237,242,243,255,259,282]. Nearly all the studies on prevalence considered in this review indicated that improving people's hygiene habits, primarily hand washing, is essential to reduce parasitic protozoan infection prevalence. In this respect, the application of the WHO WASH collection of integrated prevention and control strategies for infectious diseases, including handwashing among the most effective prevention measures [28, 101, 110, 300], represents a valuable tool for decreasing the public health burden of protozoan infections. The WASH strategies also include making available safe water sources and clean toilets. These were found to decrease the occurrence of diarrhea by 15 to 50%. Washing hands with soap can reduce up to 40% of non-emergency diarrcal cases. WASH application allowed a 27 to 56% reduction in diarrhea occurrence in children younger than 5 years of age in low-income countries, e.g., giardiasis in rural Bangladesh, with handwashing as the most effective long-term intervention. Moreover, a point-of-use drinking water filter reduced the occurrence of _Cryptosporidium_ infection in children in Rwanda. Finally, wider adoption of effective water sanitization methods, such as UV light and ozone disinfection, would effectively reduce protozoanocyst contamination of drinking water. Some ongoing trends in protozoan foodborne and waterborne infection prevalence can be inferred from this review. In particular, _C. parvum_ appeared to become increasingly dominant over _C. hominis_ in waterborne outbreaks according to reports from France and Italy [9, 122]. _C. parvum_ was also more frequent in infections originating from fresh produce [133, 132, 89, 100] and was implied in 90% of infection cases in Sweden [100]. This tendency indicates a strong implication of the contamination of animal origin in recent cryptosporidiosis cases. Therefore, the necessity to implement a One Health intervention strategy to reduce the prevalence of _C. parvum_ in farmed animals should be persecuted to prevent pollution deriving from farming activities on the contamination of tap and irrigation water. According to recent reports, the improved vigilance on cryptosporidiosis cases in some countries, mostly the Netherlands, France, and Sweden [9, 100, 121, 90], will provide novel indications on the primary sources of _Cryptosporidium_ spp. and fill knowledge gaps regarding their transmission. This new direction was made possible by the introduction of molecular typing methods which proved essential to establish epidemiological links to infection sources and reservoirs [9, 131, 132]. Regarding _G. intestinalis_, a global meta-regression showed a decreased risk of infections over time [140] probably connected to an improvement of hygiene practices, that could be linked to a reduced transmission rate by infected food handlers. However, recently, waterborne outbreaks reported in developed countries [154] can only be prevented through intensified monitoring of water treatment plant efficiency. _T. gondii_ showed a still widespread distribution based on recent monitoring activities [165] and an increase in cases was reported in Brazil, with the largest outbreak ever reported and other smaller outbreaks [168, 169, 170].