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typhoid fever
- 1. Typhoid Fever By: Aya Gamal Abdel Nasser Ahmed As an Example of mechanical vector transmission
- 4. Typhoid fever was the scourge of 19th- and early 20th-century armies. During the Spanish- American War (1898) and the Anglo-Boer War (1899- 1902), typhoid killed more soldiers than enemy bullets. concluded that, next to human contact, the housefly (Musca domestica) was the most active agent in the spread of the disease. British medical officers in South Africa, facing even worse typhoid epidemics, reached the same conclusion. The experiences of the American and British armies finally convinced the medical profession and public health authorities that these insects conveyed typhoid.
- 7. EPIDEMIOLOGY Incidence decrease with age due to acquisition of immunity by clinical and subclinical infection. • 26 million and 5 million illnesses globally. • 215 000 deaths annually. • Antimicrobial therapy has reduced typhoid case - fatality rates from 15%–20% to <1%.
- 8. EPIDEMIOLOGY Hot humid atmosphere Increase of fly population Increase in outdoor recreation and consumption of food outside home.
- 9. EPIDEMIOLOGY •In countries where water and sanitation are substandard. •Most cases in developed countries now are acquired abroad or imported typhoid cases by immigrants from endemic areas. •In Egypt, the disease is endemic. Governorates with the highest rates of disease include Assuit, Sohag, Behira, Sharkia.
- 10. EPIDEMIOLOGY A woman called Mary Mallon (1869-1938) who is known as Typhoid-Mary was a house cook who infected nearly two dozen people with the disease. Mary was a carrier of typhoid and didn't know it and by being a cook she could have contaminated the food she prepared for her employers. The breakouts of typhoid were later connected to Mary and she was put in a sanitarium against her will for the rest of her life so she couldn't contaminate anyone else.
- 11. AGENT Salmonella enterica •Serovar typhi . •Serovars paratyphi A, B, and C. •Somatic O Ag •Flagella H Ag •Vi virulence Ag Killed by heat, dryness, pasteurization and disinfectants.
- 12. Reservoir Chronic Carrier: Sheds typhoid bacilli for more than 12 months after onset of acute illness; or had the disease more than 1 year previously, but has two feces or urine cultures positive for S. typhi separated by 48 hours. Convalescent Carrier: Sheds typhoid bacilli for 3 or more months after onset of acute illness.
- 13. Outlet •Gastrointestinal tract where the organisms are liberated in feces. •Urinary tract through urine.
- 14. 1. Mechanical vector. 2. common vehicle. 3. Indirect contact. Mode Of Transmission
- 15. Inlet Gastrointestinal tract through mouth.
- 16. • General. • In endemic areas, preschool and children are more susceptible while in non-endemic areas , any age could be affected. • Individuals with gastric achlorhydria or HIV positive are more susceptible. •From the 1st week throughout convalescence (as long as bacilli appear in excreta). •About 10% of untreated typhoid fever patients will discharge bacilli for 3 months after onset of symptoms , and 2-5% become permanent carriers. • 8-14 days for typhoid fever. • 1-10 day for paratyphoid fever.
- 17. Post-infection immunity After discharge, patients should be monitored for relapse or complications for 3 months after treatment has commenced. 5-10% of patients treated with antibiotics experience relapse of typhoid fever after initial recovery. Relapses typically occur approximately 1 week after therapy is discontinued. A relapse of typhoid fever is generally milder and of shorter duration than the initial illness. In rare cases, second or even third relapses occur. Notably, the relapse rate is much lower following treatment with the new quinolone drugs, which have effective intracellular penetration. Previous infection does not confer immunity. In any suspected relapse, infection with a different strain should be ruled out.
- 19. Prevention Inactivated whole cell vaccine Vi conjugate polysaccharide vaccine Oral Ty21a vaccine Type Heat-phenol inactivated Vi polysaccharide S.typhii Live-attenuated S.typhii Ty21a MOT SC SC Oral : one capsule Number of doses 2 1 3 Interval 4 weeks - 2 days Booster if needed Every 3 years Every 2 years •Every to travelers of endemic areas •Every 5 years to those living in endemic areas . ADR Local : pain, swelling, tenderness. Systemic: fever. Not significant Not significant Minimum age of administration 6 mon 2 years 6 years
- 20. People at high risk 1. Typhoid fever vaccination may be offered to those travelling to destinations where the risk of typhoid fever is high, especially individuals staying in endemic areas for >1 month and/or in locations where antibiotic-resistant strains of S. typhi are prevalent. 2. Those who are living in endemic areas. 3. House hold members of carriers. 4. Clinical microbiology technicians.
- 21. References • Essentials of community medicine by Alexandria community medicine department staff members. • https://www.iamat.org/country/egypt/risk/typhoid-fever • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3959940/ • http://entnemdept.ufl.edu/fasulo/vector/chapter_02.htm • https://www2.health.vic.gov.au/public-health/infectious- diseases/disease-information-advice/typhoid-and-paratyphoid • https://courses.lumenlearning.com/microbiology/chapter/modes- of-disease-transmission/ • http://emedicine.medscape.com/article/231135-followup • http://www.who.int/ith/vaccines/typhoidfever/en/
Editor's Notes
- Arthropods are probably the most successful of all animals. They are found in every type of habitat and in all regions of the world. They feed on a wide variety of plant and animal materials and have been known as major causes of disease for centuries. Insects are referred to in the Chinese, Greek, Roman and other historical writings. Insect-transmitted diseases have killed more soldiers than all military actions combined. Fleas, lice and mosquitoes infect humans and domesticated animals directly or indirectly with the organisms of many dangerous diseases. Arthropod stings or bites are occasionally fatal to humans. Their germ-laden saliva or contaminated bodies also are potential sources of disease transmission. Arthropods, especially insects, are vital players in the transmission of certain diseases to humans.
- VECTOR-HOST RELATIONSHIPS In considering transmission of disease-causing organisms, it is important to understand the relationships between the vector (the disease-transmitting organism, for example, an insect), the disease pathogen (the infecting organism, for example, a virus) and the human or animal host. Pathogens that undergo changes in life stages within the vector before being transmitted to a host require the vector. Without the vector, the disease life cycle would be broken and the pathogen would die. Some diseases that require an insect host may require several individual hosts before completing pathogen transmission. In the various phases of the process, the hosts may be different species. Public-health personnel can better design and manage control programs for a particular problem by understanding how a disease is transmitted and the involvement of vectors. Myiasis. Infestation of an animal, including humans, by living maggots deposited on the skin or in a wound by flies is termed "myiasis." Some forms, such as bot flies, breed solely in this manner. Screwworm infestations of livestock and occasionally humans are examples of this phenomenon. In the U.S., the primary screwworm fly has been eradicated by integrated pest management (IPM) technology, but the less economically important secondary screwworm fly still invades the flesh of wild animals such as deer. Biological transmission of disease. Disease-causing pathogens need help to move from one host to another. Many ticks and insects are important vectors of biologically transmitted diseases. The arthropod acquires the pathogen from one host. The pathogen then develops in the arthropod's body and is transmitted to another host. Within the arthropod, the pathogen may or may not multiply. If the pathogen or parasite that causes the disease undergoes the sexual portion of its life cycle in a host, that host is the primary or definitive host, as in the mosquito that harbors malaria. For malaria, a human is the intermediate host in which the asexual stages of the parasite are found. Mechanical transmission of disease. Mechanical transmission of disease pathogens occurs when a vector transports organisms, such as bacteria that cause dysentery, on its feet, body hairs and other body surfaces to the host. There is no multiplication or development of the pathogen within the vector's body. For example, the house fly, Musca domestica, is a passive (mechanical) transmitter of bacillary dysentery. Mechanical transmission can be considered more or less accidental
- Typhoid fever, also known as enteric fever, is a potentially fatal multisystemic illness caused primarily by Salmonella enterica, subspecies enterica Serovar typhi and, to a lesser extent, related Serovars paratyphi A, B, and C. The protean manifestations of typhoid fever make this disease a true diagnostic challenge. The classic presentation includes fever, malaise, diffuse abdominal pain, and constipation. Untreated, typhoid fever is a grueling illness that may progress to delirium, intestinal hemorrhage, bowel perforation, and death within 1 month of onset. Survivors may be left with long-term or permanent neuropsychiatric complications. S typhi has been a major human pathogen for thousands of years, thriving in conditions of poor sanitation, crowding, and social chaos. It may have responsible for the Great Plague of Athens at the end of the Pelopennesian War. The name S typhi is derived from the ancient Greek typhos, an ethereal smoke or cloud that was believed to cause disease and madness. In the advanced stages of typhoid fever, the patient's level of consciousness is truly clouded. Although antibiotics have markedly reduced the frequency of typhoid fever in the developed world, it remains endemic in developing countries. S paratyphi causes the same syndrome but appears to be a relative newcomer. It may be taking over the typhi niche, in part, because of immunological naivete among the population and incomplete coverage by vaccines that target typhi. Note that some writers refer to the typhoid and paratyphoid fever as distinct syndromes caused by the typhi versus paratyphi Serovars, while others use the term typhoid fever for a disease caused by either one. We use the latter terminology. We refer to these Serovars collectively as typhoidal salmonella. Risk The bacteria are present in many Southeast Asian countries as well as in Africa, Central and South America, and Western Pacific countries in areas where there is poor water and sewage sanitation. Floods in these regions can also quickly spread the bacteria. All travelers going to endemic areas are at risk, especially long-term travelers, adventure travelers, humanitarian workers, and those visiting friends or relatives in areas with poor sanitation. Note that original infection does not provide immunity to subsequent infections. Typhoid fever, also known as enteric fever, is a potentially fatal multisystemic illness caused primarily by Salmonella enterica, subspecies enterica Serovar typhi and, to a lesser extent, related Serovars paratyphi A, B, and C. The protean manifestations of typhoid fever make this disease a true diagnostic challenge. The classic presentation includes fever, malaise, diffuse abdominal pain, and constipation. Untreated, typhoid fever is a grueling illness that may progress to delirium, intestinal hemorrhage, bowel perforation, and death within 1 month of onset. Survivors may be left with long-term or permanent neuropsychiatric complications. S typhi has been a major human pathogen for thousands of years, thriving in conditions of poor sanitation, crowding, and social chaos. It may have responsible for the Great Plague of Athens at the end of the Pelopennesian War. The name S typhi is derived from the ancient Greek typhos, an ethereal smoke or cloud that was believed to cause disease and madness. In the advanced stages of typhoid fever, the patient's level of consciousness is truly clouded. Although antibiotics have markedly reduced the frequency of typhoid fever in the developed world, it remains endemic in developing countries. S paratyphi causes the same syndrome but appears to be a relative newcomer. It may be taking over the typhi niche, in part, because of immunological naivete among the population and incomplete coverage by vaccines that target typhi. Note that some writers refer to the typhoid and paratyphoid fever as distinct syndromes caused by the typhi versus paratyphi Serovars, while others use the term typhoid fever for a disease caused by either one. We use the latter terminology. We refer to these Serovars collectively as typhoidal salmonella. Risk The bacteria are present in many Southeast Asian countries as well as in Africa, Central and South America, and Western Pacific countries in areas where there is poor water and sewage sanitation. Floods in these regions can also quickly spread the bacteria. All travelers going to endemic areas are at risk, especially long-term travelers, adventure travelers, humanitarian workers, and those visiting friends or relatives in areas with poor sanitation. Note that original infection does not provide immunity to subsequent infections.
- Epidemiology Each year, typhoid and paratyphoid fever, respectively, cause an estimated 26 million and 5 million illnesses globally. Both are enteric fevers, which are acute systemic infections caused by Salmonella enterica serotypes Typhi and Paratyphi A and B (and rarely C) that cause an estimated 215 000 deaths annually. Antimicrobial therapy has reduced typhoid case-fatality rates from 15%–20% to <1%. Mortality/Morbidity With prompt and appropriate antibiotic therapy, typhoid fever is typically a short-term febrile illness requiring a median of 6 days of hospitalization. Treated, it has few long-term sequelae and a 0.2% risk of mortality. Untreated typhoid fever is a life-threatening illness of several weeks' duration with long-term morbidity often involving the central nervous system. The case fatality rate in the United States in the pre-antibiotic era was 9%-13%.
- Person: The incidence is more among children particularly those in schooland young adults (5-19 years) Incidence decrease with age due to Incidenc decrease with age due to acuiry of immunity by clinical and subclinical infection of immunity by clinical and subclinical infection. Males more exposed to infection than females.
- Time : Seasonal pattern incidence increase in summer due to: The hot humid atmosphere. Increase of fly population. Increase in outdoor recreation and consumption of food outside home.
- Place: In countries where water and sanitation are substandard. Most cases in developed countries now are acquired abroad or imported typhoid cases by immigrants from endemic areas. In Egypt, the disease is endemic. Governorates with the highest ratesof disease include Assuit, Sohag, Behira, Sharkia.
- Reservoir: The reservoir is man as cases or carriers for both. Site: Human gallbladder carriers and, rarely, human urinary carriers. Convalescent Carrier: Sheds typhoid bacilli for 3 or more months after onset of acute illness. Chronic Carrier: Sheds typhoid bacilli for more than 12 months after onset of acute illness; or Has no history of typhoid fever or had the disease more than 1 year previously, but has two feces or urine cultures positive for S. typhi separated by 48 hours.
- Exit: Gastrointestinal tract where the organisms are liberated in feces. Urinary tract through urine.
- Mode of transmission: Flies may cause human infection through transfer of the infectious agents from excreta to foods. (Mechanical vector transmission) The typhoid bacillus is transmitted by consumption of contaminated food or water. Occasionally, direct faecal–oral transmission may occur. Shellfish taken from sewage-polluted areas are an important source of infection; transmission also occurs through eating raw fruit and vegetables fertilized by human excreta and through ingestion of contaminated milk and milk products. Pollution of water sources may produce epidemics of typhoid fever when large numbers of people use the same source of drinking-water. (Common vehicle) In low standard of personal hygiene, contacts with patients or carriers lead to contamination of the hands of the susceptible contacts then transmission of the bacilli to the mouth. (Indirect contacts)
- Susceptibility: General. In endemic areas, preschool and children are more susceptibile while in non-endemic areas , any age could be affected. Individuals with gastric achlorhydria or HIV positive are more susceptible. Post-infection immunity: After discharge, patients should be monitored for relapse or complications for 3 months after treatment has commenced. Five percent to 10% of patients treated with antibiotics experience relapse of typhoid fever after initial recovery. Relapses typically occur approximately 1 week after therapy is discontinued, but relapse after 70 days has been reported. In these cases, the blood culture results are again positive, and high serum levels of H, O, and Vi antibodies and rose spots may reappear. A relapse of typhoid fever is generally milder and of shorter duration than the initial illness. In rare cases, second or even third relapses occur. Notably, the relapse rate is much lower following treatment with the new quinolone drugs, which have effective intracellular penetration. S typhi and S paratyphi rarely develop antibiotic resistance during treatment. If an antibiotic has been chosen according to sensitivities, relapse should dictate a search for anatomic, pathologic, or genetic predispositions rather than for an alternate antibiotic. Previous infection does not confer immunity. In any suspected relapse, infection with a different strain should be ruled out. Untreated survivors of typhoid fever may shed the bacterium in the feces for up to 3 months. Therefore, after disease resolution, 3 stool cultures in one-month intervals should be performed to rule out a carrier state. Concurrent urinary cultures should be considered. Incubation period: 8-14 days for typhoid fever & 1-10 day for paratyphoid fever. Period of communicability: From the 1st week throughout convalescence (as long as bacilli appear in excreta). About 10% of untreated typhoid fever patients will discharge bacilli for 3 months after onset of symptoms , and 2-5% become permenat carriers.
- Proper water sanitation. Proper sewage disposal. Proper food House flies control. Health education
- Contraindications and precautions Both typhoid vaccines are safe and there are no contraindications to their use other than previous severe hypersensitivity reactions to vaccine components. Proguanil, mefloquine and antibiotics should be stopped from 3 days before until 3 days after the administration of Ty21a. These vaccines are not recommended for use in infant immunization programmes due to insufficient information on their efficacy in children under 2 years of age. Recommended for: Typhoid fever vaccination may be offered to those travelling to destinations where the risk of typhoid fever is high, especially individuals staying in endemic areas for >1 month and/or in locations where antibiotic-resistant strains of S. typhi are prevalent. Measures towards contacts: Immuniztion Surveillance Food handling: Family contacts may be transient or permenant carriers. Household and close contacts should not be employed in sensetive occupations e.g.food handlers until at least 2 negative feces and urine cultures taken at least 24 hours apart,are obtained. Health education Investigation of source of infection.