**4. Control**

#### **4.1 Changing transmission patterns**

Distribution and transmission patterns for some of the zoonotic trematodes may be changing for various reason. Climate plays an important role in the transmission of many infectious diseases; it not only determines spatial and seasonal distributions, but influences inter-annual variability, including epidemics, and long-term trends [108]. Evidence of climate change includes the instrumental temperature record, rising sea levels, and decreased snow cover in the Northern Hemisphere [109]. One of the most conspicuous effects of climate is an increased frequency of extreme weather conditions, which can have devastating effects on the snail fauna in some vulnerable habitats and at least temporarily affect schistosome transmission [110]. Obviously, one of the key factors for changing transmission patterns would be temperature changes [111].

Another possibility for changing transmission patterns is introduction of intermediate hosts into new areas. There are numerous examples of snails spreading over long distances and becoming invasive. Although snails may be spread over short distances attached to other animals, in mud on feet of birds or over somewhat longer distances passing alive through the digestive channel of migratory birds, the major mean of transport is the global trade in aquatic animals and plants [108]. Asian species such as *Tarebia granifera* have spread to South Africa, *Biomphalaria straminea* from South America to Asia, *Indoplanorbis exustus* to sub-Saharan Africa, and many other examples. Apple snails were introduced to Asia for food production. Invasive species could have major impact on local biodiversity. Another reason could be parasite introduction with imported final hosts or parasites change genetically and thereby perhaps be able to use new species as intermediate hosts. Gibbs [112] listed six interconnected parameters that have increased the rate of emerging diseases including: (1) global trade and tourism; (2) speed of mass transportation; (3) exposure to new pathogens through ecosystem disruption; (4) intensification and monoculture in farming; (5) sophistication of food processing, and (6) evolutionary pressures through overpopulation.

#### **4.2 Control**

Control of the zoonotic trematode-caused diseases in people and animals must depend on the severity of pathology caused, transmission patterns, and available

options for medical treatment of infection. For most of these infections, effective control needs to take a holistic approach following One-Health principles [113].

While recognizing that existing approaches to the control of zoonotic diseases will continue to benefit from their current vertical or horizontal structure, there is growing evidence for the benefits of a joint human and animal health approach [114]. The One Health concept integrates human and animal health resources and should be promoted, because many zoonoses can be better surveyed, diagnosed and controlled by considering human and animal health together [114]. In our view, the One-Health approach must take a holistic approach where all aspects of the parasite life cycle are considered and this is especially the case for zoonotic trematodes. Some of the zoonotic trematodes are closely linked to food production, and this is especially important in least developed countries.

Disease control programmes are typically integrated as there is a need to link surveillance, monitoring, and reporting all activities with actions taken by the health system and this is particularly the case for control of zoonotic diseases [114]. Such approaches may be biomedical (drug or vaccine), vector or intermediate host control (insects or snail), environmental, legislative (inspection and condemnation of infected products at slaughterhouses) or educational [114].

Some of these zoonotic trematode-caused diseases are serious problems of both public health and veterinary importance. Although infections by some of these trematodes in the final hosts can be effectively reduced through medical treatment, reinfection appears very quickly [36, 110, 115, 116]. Thus, it is necessary to take a holistic approach to control. Treatment of infections by trematodes involves the understanding of the multiple host species, environmental control, and behavior modifications and includes several scenarios. Interventions should include (1) attempts to reduce the contamination of water bodies with trematode eggs; (2) attempts to reduce the chance of eggs or miracidia infecting the first intermediate host and (3) attempts to reduce the likelihood that cercariae or metacercariae infect a final host [113].


*Zoonotic Trematode Infections; Their Biology, Intermediate Hosts and Control DOI: http://dx.doi.org/10.5772/intechopen.102434*

Combining mass drug administration, provision of clean water and maintenance of good sanitation and hygiene, community health education towards modification of risky behaviors, surveillance, and veterinary public health interventions have been shown to be effective in combatting foodborne trematodiasis [119]. Finally, there is a need to reduce dependency on chemical compounds for control of the first intermediate hosts due to their costs and low sustainability, while management procedures could be more sustainable and long lasting.
