Examples of Spread of Emerging Pathogens - Term Paper Example

AR «Examples of Spread of Emerging Pathogens» Contents Introduction 3 Factors giving rise to Emerging Pathogens 3 References 14 Emerging Pathogens Introduction In the world today it is seen that the diseases are increasing in number. Although new drugs are being introduced to tackle these diseases it is seen that these new diseases do not tend to stop. Researchers put forward different theories regarding this increasing number. Emerging pathogens are one of the most potent of all these causes which are believed to be causing these diseases. A pathogen is any substance or microorganism which has the potential to cause a disease. An emerging pathogen can be defined as a new pathogen arising in the general population of this world because of different processes undergone by the pathogen. Pathogens are emerging in the society because of adaptation, global patterns of travel, increased contact with animals, and vector interactions. Because these pathogens are new in the society it becomes quite difficult to control them and hence they cause specific diseases in the society. West Nile Virus (WNV), Severe Acute Respiratory Syndrome (SARS), Human PapiloVirus, Avian influenza, Vibrio cholerae O139, Escherichia coli , Campylobacter jejuni are all examples of some emerging pathogens nowadays (Greenblatt & Spigelman 2003; Tapper 2006; Woolhouse & Sequeria 2005). Factors giving rise to Emerging Pathogens Emerging pathogens are arising because of different reasons in the society. It is believed that these pathogens are emerging because of many socio-economic, environmental and ecological factors. Emerging pathogens have entered the society in which they were previously not known. Because of increased travel pathogens from one area can be travelled to another if a person is acting as a reservoir. Some diseases or pathogens were previously prevalent in small villages and were unknown to the society as a whole but as time has passed by it is seen that these pathogens have entered the arena as a whole. Pathogens are transmitted from animals too and it is seen that animals are more in contact with the human beings now. Previously many diseases were believed to be entering the society from animals such as tuberculosis and HIV. Thus these emerging pathogens are coming in the society from other species (Fine 2006; Daszak 2000). Ecological conditions also matters when it comes to the increase in emerging pathogens. Some areas previously were not cultivated but as they are being cultivated now it is seen that the pathogens are entering the area where these lands are being cultivated. Landscapes are also important through which the pathogens are rising. Different changes in landscapes are causing vectors to arise in those areas and hence the hosts are increasingly being affected. The prevalence of diseases was low in olden times but as these landscapes have changed the number of emerging pathogens have also increased (Taylor 2001). The socio-economic factors revolve around countries which are underdeveloped. Many diseases get a perfect environment in these underdeveloped countries because of the unhygienic conditions persisting over there. Immunization is also not practiced in these underdeveloped countries as it is prevalent in the developed countries and hence emerging pathogens have a way through which they can enter the population. Microorganisms have a special characteristic of adapting to different environments and getting resistant to the new drugs. As new drugs are being introduced in the society it is seen that the microorganisms get adapted to the characteristics of the new drugs. In other words they change their structure such that they cannot be destroyed. This leads to new strains of bacteria which can emerge as new pathogens in the society. Hence the adaptation characteristic of the bacteria also helps them to create new pathogens in the society (Schmidt 2000; Morens et al 2004). Waterborne Emerging Pathogens Many of the emerging pathogens nowadays are waterborne i.e. they take birth in water. Cholera has been a known disease in the world and two emerging waterborne pathogens are Vibrio cholerae O139 and Escherichia Coli (E.coli O157:H7). E.coli has not only become a problem for the underdeveloped nations but has also become a problem for the developed ones. This bacterium would be discussed subsequently. Vibrio Cholerae O139 is a pathogen which first infected many of the people living in Asia. It started in Bengal and then spread to India in 1992 from where it entered the vicinities of Thailand. It is through different methods that these emerging pathogens are spreading all over the world giving a difficult time to the authorities who have not handled such cases previously (Sharma et al 2003; Smolinski et al 2003). E.Coli a lethal emerging pathogen Escherichia coli (E. coli) are bacteria referred to as an enterobacteriacea, that is they exists normally in the intestine of human and animals. E.coli is an emerging pathogen which is affecting many parts of the world. This bacteria exists in the form of gram negative rods and is named for the man, who discovered them, Theodor Escherich, in 1885. E. coli has been associated with many pathological conditions which include the inflammation of the gall bladder, inflammation of the biliary tract, infections of the urinary tract and blood, as well as diarrhea, particularly traveler’s diarrhea. Newborns are also affected and typically present with inflammation of the meninges. Though this inflammation has also been reported in adults but it is more common in new born children and it usually occurs in adults as a result of invasive procedures. The respiratory tract might also be involved with resultant pneumonia. E. coli infection stem from various different sources: E. coli are present in patient’s own colonic flora; E. coli causing neonatal meningitis are present in mother’s birth canal; and those that causes traveler’s diarrhea are present in food or water (Levinson 2008; Robbins et al 2005; Ramana, 2004). Characteristics of E.coli E. coli is considered an aerobic bacterium, though not completely aerobic. They can survive in the presence of oxygen and it also has the capability to exist in the absence of oxygen, anaerobic, by the process of fermentation. E. coli also has the property of movement though there are certain forms of the bacteria that form exceptions and do not move. The mobility is provided by flagella, which are referred to as peritrichous flagella, present on all sides of the bacteria. The bacterium does not have the property of forming spores; and has three antigens present. The antigen present on the cell wall of the bacteria is the “O” antigen, the antigen present on the flagellum is the “H” antigen, and finally the antigen found on the capsule of the bacteria is the “K” antigen. These antigens have great variability with each of them existing in many different forms. This is the reason that E. coli exists in many different forms. This bacterium is responsible for infections of the urinary tract in 50 percent women in the United States. This is because there is a greater disposition towards females of this infection owing to the increased hospital visits related to deliveries and their higher susceptibility during the child bearing period. But this pattern is different for the newborns in which the rate of the infection of the urinary tract is higher in male children than in females. E. coli is also listed as an infection which occurs in the hospital settings and has been associated with an average of 31 percent hospital acquired infections in the United States as well as a cause of diarrhea in 4 percent of the people. The meningeal inflammation that results due to E. coli should not be overlooked because it accounts for 8 percent of the deaths due to this condition and it can also result in pathological conditions of the nervous system (Ramana 2004; Levinson 2008). Waterborne E.coli O157:H7 Enterohemorrhagic Escerichia coli (EHEC) O157:H7 is the full name of the bacterium E. coli O157 which is a food and waterborne pathogenic strain of bacterium E. coli. The bacteria E. coli O157 was first known as a result of gastrointestinal illness in the early 1980s. E. coli O157 is different from other pathogenic E. coli in different ways like , E. coli O157 is sorbitol negative whereas 93 % of the E. coli ferment sorbitol, E. coli O157 does not produce heat stable toxin but some type of E. coli do produce it, E. coli O157 cannot hydrolyze 4-methylumbelliferyl -β-D-glucuronide while other strains can. The E. coli O157 strain is most closely related to K12 strain, as they share a common backbone. These two strains are just about identical in gene sequence and also in length, but O157 at one specific point the base pairs of genes are reversed. There are hundreds of sections of DNA in each genome, 1.34 megabases code for 1,387 genes in the O strain called O islands and 0.53 megabases code for 528 genes in the K strain known as K islands. The O157 strain only has 40% of the acquired genes, meaning 561 of 1387 genes can be assigned a function. There are 3574 protein- coding regions in the backbone and the average nucleotide identity is 98.5% between O157 and K12 (Perna 2001; Ramana 2004). E. coli O157 is also a water-borne strain which can also be found in water. Usually the source from where the water is contaminated by the bacteria E. coli is animal waste and sewage connection. This animal waste and sewage connection already consists of the bacterium and may infect the whole supply of drinking water to human beings. Prevention strategies have thus been formulated to check the level of contamination of water supply. Laboratory diagnosis can be carried out to check if water is contaminated with the bacteria or not. The contaminated water can be purified by killing the E. coli present in the water. The purification of the water can be done by treating the water with chlorine or ultraviolet light (Ramana 2004). E Coli O157:H7 is a strain which cannot cause illness in the animals but can cause them to be carriers of the bacteria. It has been found that this strain is usually transmitted into human beings via the animals who are affected by this bacterium. This strain of E coli can be found in cattle, sheep, pigs, deer, dogs and poultry. In order to find out as to which animal has this strain, their feces can be tested which would show a positive sign of this bacterium. Animals particularly catch E. Coli O157:H7 by consuming the bacteria which is found in the feces of the infected animals. Anything which would be affected by this bacterium may cause the strain to enter the animal’s body which can then act as a carrier. It is believed that E.Coli O157:H7 does not cause any apparent illness or defect in the animal upon which it acts. Moreover the effect on animals can be minimized if the animals are given proper care and are kept away from contaminated feces and water. If the strain is not ingested by the animal from any source then the animal will not act as a carrier for this strain (Todd 2007). E. coli has different components giving it the propensity to cause diseases; these are; pili, capsule, endotoxin and three exotoxins. Out of the three exotoxins, two causes watery diarrhea and the other causes bloody diarrhea. When a person has food poisoning from E. coli, the first step is the attachment of the bacterium to the jejunum and ileum of the small intestine in human gastrointestinal tract, with the help of pili which are the outgrowths from the bacterial surface. Once attached to the gastrointestinal wall, the bacteria synthesize exotoxins which will act on the wall’s cells and will cause diarrhea. The bacterium E. coli can produce either of the two enterotoxins, the heat-labile toxin and heat-stable toxin. The heat-labile toxin act when the enzyme adenylate cyclase is stimulated. The addition of adenosine diphosphate-ribose to the G protein stimulates the cyclase which in turn activates the heat-labile toxin and the result will be the increased intracellular cyclic adenosine monophosphate concentration. Further this high intracellular cyclic adenosine monophosphate concentration stimulates the cyclic adenosine monophosphate-dependent protein kinase, which has the ability to phosphorolate the membrane ion transporters. The transporters take ions out of the cell which causes the outburst of fluid, calcium and potassium to the lumen of the gastrointestinal tract ensuing watery diarrhea. EHEC strains of are invasive, invading, the large intestinal epithelium causing bloody diarrhea. E. coli O157 produces exotoxin known as verotoxin, which acts by removing an adenosine from ribosomal RNA (28S), thus inhibiting protein synthesis (Sheff 1999; Levinson 2008). Causes of E.Coli O157 Some people who suffer from bloody diarrhea caused by E. coli O157 can also suffer from a syndrome known as hemolytic-uremic syndrome. This syndrome occurs because of the entrance of the exotoxin known as verotoxin into the bloodstream. In this syndrome the patient suffers from hemolytic anemia, thrombocytopenia and renal failure. Anemia is a condition in which the patient’s blood is deficient in red blood cells or hemoglobin so hemolytic anemia is that anemia which occurs due to the breakdown of red blood cells. The endothelium of the small blood vessels contains receptors for vertoxin. When the vertoxin enters the bloodstream it binds to the receptors present on the surface of the endothelium. The vertoxin will then destroy the endothelium to which it is attached and will cause hemolysis which means breakdown of red blood cells and release of hemoglobin from red blood cells. When red blood cells pass through these damaged blood vessels the red blood cells get distorted and at last lysis occurs. Thrombocytopenia refers to platelets deficiency in blood. In hemolytic uremic syndrome the patient suffers from thrombocytopenia because the platelets adhere to the already destroyed epithelium by vertoxin. Eventually the amount of functional platelets diminishes causing thrombocytopenia. The surface of the epithelium of kidney also has the receptors for vertoxin and by binding with the receptors, vertoxin destroys the kidney epithelium. The destruction of kidney epithelium leads to acute renal failure (Levinson 2008; Ramana 2004 Stephen et al 2004). Examples of spread of emerging pathogens In 2006, biggest food-borne diseases were spread in Canada by the fresh spinach contaminated with E. coli. More than 200 people got sick and three deaths occurred and 31 cases of hemolytic uremic syndrome were reported. The causes of the diseases were contamination of the spinach and the environmental risk factors for the contamination were the presence of pigs in the nearby areas, and surface waterways exposed to feces from cattle. And the precise way by which the spinach got contaminated still remain unknown because the spinach was contaminated before the investigation started (E. coli cases down in 2009, CDC says; Todd 2007). Another example of an outbreak of E.coli, 2 people died and 28 fell ill during spread of a strain of E. coli in ground beef, three of them developed kidney failures. However recently it has been found that the cases of E.Coli have decreased in number because of increased preventive measures. A report by CDC has shown that cases of the E.Coli strain which were previously very common in states were reduced in number from their previous infections. A 12% decrease in the number of infections has been noticed since 2008 (Money Times 2010). Control of Emerging Pathogens The question now arises as to how these emerging pathogens can be controlled from entering the society. It is believed that not much can be done when it comes to controlling or preventing these emerging pathogens. The reason for such a belief is that pathogens are changing their nature everyday because of their adaptation capabilities and these things cannot be restricted. Other than that travelling is a phenomena of the world which cannot be stopped but can rather be surveillance for these pathogens. But here again if a person is acting as a reservoir for the pathogen then it may be difficult to control this emerging pathogen from entering the new society. Animal contact cannot be reduced as such so that the diseases do not enter the society. However some measures have been proposed to control or prevent these emerging pathogens from entering the society. Surveillance is the first and foremost option to eradicate these emerging pathogens as they are entering the society. Surveillance can be done in several ways which can help the society to take a stand on the emerging pathogen. Surveillance can be done in individuals who are most prone to the new pathogens such as farmers and shepherds or individuals who have more interaction with the animals. Surveillance should be carried out all over the world in areas which have been neglected in the past. This would help to contain any emerging pathogen which is in the villages now but may have the potential to spread further in the world. Surveillance can be done in animals and it can be found out as to which pathogen can affect the human beings. This surveillance can help the researchers to take notes and make a policy which would help to contain the pathogen from spreading. Documenting the resources would help the researchers greatly as they would be able to isolate the pathogen and learn about it more if it is found beforehand. The ways through which the emerging pathogen may spread in the society should also be monitored. These ways should then be checked regularly upon by the authorities so that the pathogen does not in any way enter the hosts through these ways. For example many pathogens are spread through water and in such a case the authorities should manage the water properly so that the pathogen does not spread (Pasculle & Synder 2010). A policy should be implemented by the authorities through which they decrease the contact of human beings with animals. Many of the pathogens have spread into the human population because of these animals and such a policy would greatly reduce the risks of new pathogens from entering the society. The next step would be to disinfect the respective resources which are involved in the transmission of emerging pathogens. Disinfection of the emerging pathogens can be done by applying some chemical or method to the route from where the pathogen may emerge in the society. For example if Cryptosporidium enters the water then it can be disinfected by the use of ultraviolet radiation. This ultraviolet radiation along with chlorination can destroy the pathogen and thereby prevent its spread in the society. Knowing about the pathogens before they enter a society is very important for the researchers so that they can know enough about the pathogen. With such information they can contain the spread of emerging pathogen even after it has entered the society. The use of antibiotics is playing a great role in the adaptation characteristics of the bacteria and hence this use should be reduced or somehow a new methodology should be sought out. This new methodology should aim to reduce the cons of irregular antibiotic doses which are making the pathogens resistant to the bacteria (Gostin et al 2000; Chiodini 1996; Pasculle & Synder 2010). Conclusion It can be found out that many of these above written prevention methods are difficult to follow however many authorities have taken the responsibility to lower the incidence rates of these pathogens. The molecular studies of pathogens have increased nowadays and it is through these studies that a lot about the emerging pathogens has become known. Different factors which may increase the spread of pathogens are also known through these processes. Although it has become quite difficult to control the emerging pathogens from spreading some of the measures mentioned above are becoming successful in tackling this problem. 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