Disease Report: Cholera Cassidy Smith May 6, 2014

Transcription

1 Disease Report: Cholera Cassidy Smith May 6, 2014

2 Disease Cholera is an acute diarrheal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae (01 and 0139). It is highly virulent, and can result in death within hours of inoculation. (1) Those with compromised immunity, malnourished, or living in regions with unsanitary water sources are most susceptible to this disease. Transmission Most commonly, transmission of Cholera is through fecal-contaminated water. Thus, in more impoverished areas with weaker infrastructure, Cholera is easily widespread due to the lack of sanitation processing. Furthermore, food is a vehicle for transmission, also due to fecalcontamination. During food preparation, unsanitary food handlers can easily contaminate food ranging from seafoods, rice, fruits, vegetables, poultry, meat, and dairy products. Foods of a high-moisture content, neutral or base ph, low temperature, high organic content, and absence of competing bacteria are more susceptible to Cholera contamination. Reservoirs V. cholerae is often part of the normal flora of isolated brackish water (a mixture of salt and fresh water) and estuaries. Living reservoirs may include algal blooms, such as plankton, and humans. (3) General Characteristics of V. cholerae The causative organism, V. cholerae, 01 and 0139, is a short, curved, motile, aerobic, gram-negative bacillus. It produces enterotoxin, a protein that induces hypersecretion of an isotonic electrolyte solution by the small-bowel mucosa. These organisms do not invade the intestinal wall thus, few to none WBC are present in stool samples. (4) Key tests for identification (specific) The most definitive testing for Cholera is a stool sample test. Using symptoms as diagnosis will often be inaccurate because many other pathogenic diseases reflect similar symptoms, especially acute diarrhea. Cary Blair media is ideal for transport, and the selective thiosulfate citrate bile salts agar (TCBS) is ideal for isolation and identification. Additionally, areas with limited or no laboratory testing may utilize the rapid test method of the Crystal VC dipstick. This rapid test can provide an early warning of a cholera outbreak, that may be beneficial to proactive containment. However, the sensitivity and specificity of this test is not optimal thus, if available, laboratory testing is always preferable and most accurate. (2) Signs and symptoms of disease A brief incubation period of one to three days is typically followed by mild symptoms of painless, watery diarrhea, increase in heart rate, low blood pressure, and vomiting. Symptoms quickly escalate with the increasing virulence as severe dehydration leads to intense thirst, oliguria (low urine output), muscle cramps, weakness, and marked loss of tissue elasticity such as, sunken eyes and wrinkling of the skin. If left untreated, more serious issues may arise like circulatory collapse with cyanosis or renal tubular necrosis. (4) Historical Information According to the World Health Organization, the first widespread outbreak of Cholera occurred in the 19 th century from its original reservoir in the Ganges delta in India. Cholera spread rapidly due to the inadvertent transport of bilge water mainly from British ships acquired in the Bay of Bengal that contained the V. cholerae organisms. By dumping the contaminated water into their own port cites upon arrival home infected the local waters, thus an outbreak was incontrovertible, thus the rapid outbreaks throughout Europe and into Russia. The French were most likely to have infected the New World in 1832, in which the disease began to

3 spread south from Montreal and to New York City. In 1855, an endemic of Cholera broke out in London, England. Dr. John Snow identified the Broad Street water pump as the single point source of that outbreak. His detailed maps showed where people who became sick lived, proved significant enough that the only possible origin of infection was the water pump. This landmark study established an epidemiological view of cholera that had wide benefits prior to modern medicine. (6) Since the 19 th century, six pandemics have killed millions of people across all continents. Currently, the seventh pandemic began in South Asia in 1961, reaching Africa in 1971, and the Americas in Cholera is now endemic in many countries. (1) Virulence Factors The Cholera toxin, an enzyme, is the distinguishing virulence factor of strains 01 and 0139 groups solely. These enzymes initiate a prolonged hyper-secretion in the small intestine causing more intense diarrhea as the organism thrives. Diarrhea intensifies to a point where the enterocytes become fragile and begin to fall off from the basement membrane of the villus shortly after symptoms appear. Internalization of the toxin-ganglioside complex occurs. The bacterial enzyme catalyses the transfer of ADP ribose from intracellular NAD+ to the s subunit of the trimeric G protein that is normally attached to the cytoplasmic side of the plasma membrane of each enterocyte. ADP ribosylation changes the activity of s subunit so it can no longer hydrolyze its bound GTP substrate, thus deregulating cyclic AMP activity. Hypersecretion immediately ensues. Efflux in chloride and bicarbonate ions into the small intestinal lumen pulls large quantities of water with it by passive osmosis. The process continues until no more toxin is produced, or until the enterocyte is shed into the lumen of the small intestine. (Very technical explanation, 6) Control and Treatment Various methods of control and treatment are available today and widely used. In fact, 80 percent of those infected with Cholera can be treated by rehydration salts or IV fluids for more serious cases. These patients will most likely also require appropriate antibiotics to diminish the duration of diarrhea, reduce the volume of rehydration fluids needed, and shorten the duration of V. cholerae excretion. Antibiotic treatment includes Doxycycline, azithromycin, furazolidone, trimethoprim/sulfamethoxazole (TMP/SMX), or ciprofloxacin, which should be prescribed according to results of susceptibility testing. However, mass administration of antibiotics is not recommended, as it has no effect on the spread of cholera and contributes to increasing antimicrobial resistance. (1) Control and treatment is also emphasized by global efforts to maintain clean water and access to clean water for all populations. The Centers for Disease Control and Prevention s National Center for Zoonotic, Vector-Borne, and Enteric Diseases, reports that the United States, despite its relatively light burden of waterborne disease, is home to a deteriorating public drinking water distribution system, increasing numbers of unregulated private water systems, and a limited, passive waterborne disease surveillance system. (5) This sheds light on the fact that no matter the wealth of the nation, water sanitation is a global necessity that must be executed properly and consistently. (Cholera is subject to quarantine conditions under the Commonwealth Quarantine Act 1908.[3]) Prevention and vaccines Currently, there are two types of approved and effective oral Cholera vaccines that are available in over 60 countries. Both vaccines are whole-cell killed, where Dukoral contains a recombinant B-sub unit and the Shanchol without the B-sub unit. Both have protection rates over 50 percent during two year endemic settings. Furthermore, both require two doses given between

4 seven days and six weeks apart. When traveling to endemic areas, one should be advised to careful food and water consumption and personal hygiene. It is also recommended for travelers to carry oral rehydration powder (must be mixed with boiled or sterilized water) as a precautionary measure. Local cases and outbreaks Cholera first appeared in Texas in 1833 causing some deaths. However, it was far more destructive during an epidemic following in Approximately 500 deaths had occurred in San Antonio by May of that year. Cholera was much more prevalent in the United States during the 19 th century, prior to modern sewage and water treatments. (7) Global cases and outbreaks The most noted region to Cholera outbreak is the Southeast Asia region, including India and Bangladesh. Morbidity rates tripled from 2010 to 2011, and mortality rates also increased. Unfortunately this is due to a variety of factors, some of which are uncontrollable. Extreme environmental factors such as flooding from monsoon rains contribute an uncontrollable factor to the spread of Cholera, which can be further exacerbated by poor infrastructure or lack proper water sanitation. However, it the majority of African countries that hold the highest rates of mortality and morbidity of Cholera epidemics. This is almost single-handedly due to the inaccessibility to basic health care, clean water, and education on the disease.

5 Works Cited "Cholera." Media Centre. World Health Organization, n.d. Web. 03 May < Cholera (Vibrio Cholerae Infection). Centers for Disease Control and Prevention, 18 Oct Web. 03 May < Department of Health, Victoria, Australia. "Cholera." Infectious Diseases: Epidemiology and Surveillance. State Government Victoria, 10 May Web. 03 May < "Cholera: Gram Negative Bacilli." Merck Manual for Health Care Professional. Merck, n.d. Web. 03 May < Institute of Medicine (US) Forum on Microbial Threats. "Vulnerable Infrastructure and Waterborne Disease Risk." Vulnerable Infrastructure and Waterborne Disease Risk. U.S. National Library of Medicine, 18 Sept Web. 03 May < "Cholera." Medical Ecology, Web. 03 May < Burns, C.R. "Epidemic Diseases." Texas State Historical Association, n.d. Web. 03 May <