Recently, vector-borne bacterial and parasitic diseases have developed or re-developed in a lot of geographical regions inducing economic problems and global health which include livestock, companion animals, wild life and humans. Globally diseases that their transmission occurs via arthropod vectors are the main significance to the health of animals and humans. Furthermore these diseases and their epidemiology associated with a range of hosts, infectious agents and vectors. As result of an oversupply of factors, is the over time change of disease patterns that also vary from one geographic zone to another.
Infectious agents included in developing pathogens have been showed in other regions and were introduced into already unknown areas. However, agents that were continually showed on a low level or in a different host in the affected area and owning to some modification have appeared more broadly spread in the population. On the other hand those were not previously recognized and the organisms that have been classified and correlated with a new disease with an unknown etiology. Conversely, for disease such as piroplasmosis naive wildlife or domestic animals transmitted into an endemic region has resulted many times in epidemic outbreaks. Unexpected induction of disease vectors like mosquitoes or tick species originating at one area to another eventually could be reliable for the spread of infection to new regions. Over the last two decades, the progress in molecular biology has also led to a new vector-borne pathogenic organism’s discovery. These bacteria transmitted by arthropod and have been correlated with disease syndromes such as peliosis hepatis, bacillary angiomatosis, endocarditis and cat scratch disease. The most prevalent vector-borne disease that became known just over 20 years ago in North America as a new disease with a spirocheatal causative agent is the Lyme disease which has been exposing as a main pathogen of dogs and humans represented by molecular detection of historical specimens.
Clearly, climatic and demographic changes affect the global distribution of vector-borne protozoan pathogens. At first, epidemiology and ecology of vector-borne diseases are affected by three main factors constituting the host, the environment and the pathogen. Main factors that are reliable for the spread and evolution of vector-borne parasites contain modifications in irrigation habits and water storage, climate and atmospheric changes, habitat changes, public health and evolvement of drug resistance and insecticide pollution. Global or governmental or war and civil unrest management failure are also the main factors that are associated with the spread of infectious diseases. In the last two decades, the progress in epidemic understanding and planning even with the evolution of recently diagnostic molecular techniques have permitted researchers to better diagnose and trace pathogens, helped to establish intervention programs, their source and routes of infection and defensive public health. An important responsibility of veterinarians, physicians, biosecurity officers and health care workers is the future vector-borne disease prevention. A corresponding global approximation for the vector-borne disease’s prevention should be achieved by governmental agencies and international organizations in association with research institutions.
Moreover, an important factor which affects the global distribution of vector-borne protozoan pathogens is habitat change which is a result of widespread land use, agricultural development, deforestation and modifications in irrigation habits and water storage which supply new niches for vectors. Transformation and deforestation of forests to human settlements or open areas, grazing land and agricultural areas, which are result of important changes in the environment and in the structure of vectors, and thus, the induction of new pathogens. Other widespread changes, like deforestation and agricultural practices, increase the transmission risk for vector-borne disease. In the past 50 years, several irrigation systems and dams have been developed except regard to their effect on vector-borne diseases. Furthermore, agricultural practices like rice production has increased and also tropical forests are being cleared at an enhancing rate. Ideal breeding sites for domesticated mosquitoes are formed by consumer products. Products that tend to be disposed in the environment where they collect rainwater are those packaged in cellophanes, nonbiodegradable plastics and tin. An excellent mosquito breeding places are the several disposed automobile tires in the domestic environment. The global used tire industry and container shipping have conduced to the raised geographic distribution of selected mosquito species that lay their eggs in used tires. In the Thar Desert in north-western India where occurred the Plasmodium falciparum malaria evolution and Anopheles culicifacies spread and establishment which followed the development of irrigation canals. The world is encountering the development and substantial urbanization of human population. Moreover in Senegal the construction of the dam at Diama was intended to intercept the invasion of seawater into the river and as a result the salinity reduction and increased water pH thus increasing the development and fecundity of freshwater snails and the exposure of humans in the lower and middle valleys of the Senegal River Basin to Schistosoma mansoni. Development of new contacts changes in the new massively inhabited environment caused by the movement of people from rural areas to urban centers. Generally more susceptible to the endemic diseases are the newcomers to which they may not be immune. Furthermore in the new environment have the induction of new vectors and pathogens. Below these circumstances, the opportunities of parasites and vectors are increase for transmission and exchange. In past 50 years the global societal and demographic alterations have directly contributed to the vector-borne and other infectious diseases regeneration. Generally uncontrolled and unplanned urbanization in evolving countries causes the worsening of public health infrastructure, management systems of water, sewage and waste. New roads construction supplies means of vector and host transportation. As result of these changes is the formation of optimal situations for the vector-borne disease’s transmission to large populations. Finally, the jet airplane has had a profound influence on rapid global transportation. Airplane travel provides an easy means for transporting pathogens between population centers. The result is a constant movement of viruses, bacteria, and parasites among cities, countries, regions, and continents.
Also another factor that induces global distribution of vector-borne protozoan pathogens is public health. Decisions of policy for public health have greatly reduced the surveillance resources, that principally because control programs had decreased the menace of public health from vector-borne diseases as a result reduced the prevention and control of those diseases. However, the drug resistance and technical problems of insecticide which are also public health decisions, have an important function for the regeneration of diseases like malaria and dengue. The result of the cessation or merger of many programs usually are the reduced resources for infectious diseases and eventually to the worsening of the public health infrastructure needed to deal with these diseases. Moreover, after 1970 in vector-borne diseases the good training programs decreased dramatically. The lack of preventive medicine training in most medical schools is another important problem for vector-borne diseases. The medicinal emphasis and approximation on high-tech solutions to disease control have led health officials, most physicians and the public that is based on “magic bullets” to control an epidemic or cure an illness.
In addition, another factor is the alterations in temperatures and climate that affect the pathogen transmission effectiveness by vectors and the vectors distribution. As a result of human activities the atmospheric composition alters constantly, especially burning of fossil fuels. In addition is the plant water loss decrease and the increase of atmospheric carbon dioxide concentrations via evapotranspiration. Accordingly, plants are enhancing the density of plant foliage for elongated periods in the year, derive more foliage with the same amount of water and supplying more favourable microclimates for insect vectors. The greenhouse effect and stratospheric ozone layer increase destruction by the release of carbon monoxide, methane, halogenated compounds and volatile organic compounds together with upsurge in atmospheric carbon dioxide concentrations. In response to the raised global temperature the hydrological cycle has changed, as warm air can hold more moisture, and so did the waterborne disease vectors. Ticks and mosquitoes are excessively sensitive to climate and temperature alterations. Their reproduction, mortality rates and feeding activity are generally exactly associated with the environmental temperature. Finally was recommended that the spread of habitats of tropical insects into more southern and northern latitudes along with higher increases is induced by global warming.
Furthermore, pollution is another factor that affects global distribution of vector-borne protozoan pathogens. The Tropical Rainfall Measuring Mission satellite provide measurements, detected that both ice precipitation evolvement and cloud droplet coalescence were interrupted in polluted clouds. Also indicated by satellite data that industrial and urban air pollution inhibits precipitation. The precipitation onset delayed from 1.5 km above cloud base in pristine clouds to more than 7 km in pyro-clouds and more than 5 km in polluted clouds and reduced cloud droplet size by heavy smoke from the Amazon forest fires, that indicated by latter study. Pollution associated changes in rainfall first of all change vector environments and therefore, the distribution of correlated pathogens.
Eventually the last factor that induces global distribution of vector-borne protozoan pathogens is the insecticide and drug-resistance. The most important factors are first of all the extensive and inappropriate drug use and also improvement of genetic mutations. In the improvement of drug-resistant pathogens and vectors include vector movement and population between other factors.
For the re-development and sudden increase of diseases the potent drivers are the insecticide and drug resistance of parasites and vectors. Examples for the function of resistance Malaria spread are including in the following reports. Was latterly related from Saudi Arabia that chloroquine-resistant P. falciparum cerebral malaria inducing a high mortality rate, where previously malaria was contemplated chloroquine-susceptible. The increase in chloroquine resistance induces a significant rise in specific mortality of malaria in Senegal, Malawi and Zaire. During the previous decade when an outbreak of malaria has occurred in Chindwara in central India, the DDT-resistant A. culicifacies was found as the main mosquito species.
As a conclusion, the complicated correlation among disease drivers like global travel or weather, their financial and health impacts and modifications in pollution, are progressively being defined by research. In the last few decades, epidemiologic techniques and tools for the research of infectious diseases have refined importantly. The development of epidemic prediction, epidemic knowledge and the planning of policy analysis and efficient control provide tools for the use of geographic information systems (GIS), risk analyses, climate models and remote-sensing technologies in research. Furthermore, in the vector-borne pathogens the evolvement of complex diagnostic procedures and particularly the establishment of molecular techniques, mostly the evolution of the nucleotide sequencing and PCR, have permitted rapid, specific and sensitive diagnoses, which in turn accommodate timely prevention and exact treatment efforts. The evolution of new vaccines, chemotherapeutics, repellants, biological products and insecticides contrary to the main vector-borne diseases is critical for accomplishing control or elimination. Rotational therapy or multi-drug therapies should be employed contrary to parasites and vectors in case of the prevention of the evolvement of drug-resistance. Another preventative approximation such as biological pest control, in the protection of ticks and other vectors which are the essential need for the repellants and insecticides for example the use of nematodes, wasps, birds and entomopathogenic fungi that are safe for the environment. Programs for multi-national control and elimination have proven powerful in the battle against various vector-borne diseases comprising River blindness in western Africa and Chagas disease in Latin America. The association of global organizations, has a significant function in the funding and allocation of programs, such as the Untied Nations’ agencies constituting the WHO and World Bank. The significant allocations of the above associations have also made by public organizations such as philanthropic trusts and societies and private pharmaceutical companies. Also have been published risk evaluations and sustainability studies for future outbreak’s anticipation and then evolve the consequence of global alterations upon the transmission of diseases and the environment. Studies have been applicable by making suggestions for intervention and policies achievements. Nevertheless there is further requirement for bigger complication of international non-governmental evolvement and aid organizations. More global resources in the future, to the evolvement of prevention and prediction programs, should be appropriated to minimize or eliminate vector-borne diseases in evolving countries. It is essential that an allocated global rather than a single governmental approximation should be acted in vector-borne disease prevention.
References http://www.who.int/globalchange/summary/en/index5.html http://www.ecdc.europa.eu/en/healthtopics/climate_change/health_effects/pages/vector_borne_diseases.aspx http://www.pbl.nl/en/publications/2001/Climate_Change_and_Vector-Borne_Diseases__A_global_and_site-specific_assessment http://www.ncbi.nlm.nih.gov/books/NBK52939/