Paratyphoid fever overview

# Overview
Paratyphoid fevers are a group of enteric illnesses caused by strains of the bacterium Salmonella paratyphi.
There are three species of Salmonellae that cause paratyphoid: Salmonella paratyphi A, S. paratyphi B ( or S. schotmulleri) and S. paratyphi C (S. hirschfeldii). They are transmitted by means of contaminated water or food. Typhoid fever is an acute, life-threatening febrile illness caused by the bacterium Salmonella enterica serotype Typhi. Paratyphoid fever is a similar illness caused by S. Paratyphi A, B, or C. The paratyphoid bears similarities with typhoid fever, but its course is more benign.

# Causes
Paratyphoid fever is caused by any of three strains of Salmonella paratyphoid: S. paratyphoid A; S. schottmuelleri (also called S. paratyphoid B); or S. hirschfeldii (also called S. paratyphoid C).

# Differentiating Paratyphoid fever from other Diseases
Paratyphoid fever resembles typhoid fever but presents with a more abrupt onset, milder symptoms and a shorter course.

# Epidemiology and Demographics
Infections with S. Paratyphi A are common in Africa, they follow a course similar to typhoid but rose spots are more abundant and larger. Paratyphoid B is more frequent in Europe.  Paratyphoid C is a rare infection, generally seen in the Far East. An estimated 22 million cases of typhoid fever and 200,000 related deaths occur worldwide each year; an additional 6 million cases of paratyphoid fever are estimated to occur annually. Approximately 300 cases of typhoid fever and 150 cases of paratyphoid fever are reported each year in the United States, most of which are in recent travelers.

# Risk Factors
Paratyphoid fever can occur in any age group as it is food and water borne. Humans are the only source of these bacteria; no animal or environmental reservoirs have been identified. Typhoid and paratyphoid fever are most often acquired through consumption of water or food that has been contaminated by feces of an acutely infected or convalescent person or a chronic, asymptomatic carrier. Transmission through sexual contact, especially among men who have sex with men, has rarely been documented. The risk of paratyphoid fever is also increasing among travelers to southern and Southeast Asia. Travelers to southern Asia are at highest risk for infections that are nalidixic acidresistant or multidrug-resistant (resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole). Travelers who are visiting friends and relatives (VFRs) are at increased risk. Although the risk of acquiring typhoid or paratyphoid fever increases with the duration of stay, travelers have acquired typhoid fever even during visits <1 week to countries where the disease is endemic.

# Natural History, Complications and Prognosis
The serious complications of paratyphoid fever generally occur after 23 weeks of illness and may include intestinal hemorrhage or perforation, which can be life threatening. Those diagnosed with Type A of the bacteria strain rarely die from it (in rare cases of severe intestinal complications). With proper testing and diagnosis, the mortality rate falls to less than 1%.

# Diagnosis

## Physical Examination
In paratyphoid fever, liver and spleen enlargement can be seen.

## Laboratory Findings
A single blood culture is positive in only half the cases. Stool culture is not usually positive during the acute phase of the disease. Bone marrow culture increases the diagnostic yield to about 80% of cases. The Widal test is an old serologic assay for detecting IgM and IgG to the O and H antigens of salmonella. The test is unreliable but is widely used in developing countries because of its low cost. Newer serologic assays are somewhat more sensitive and specific than the Widal test but are infrequently available. Because there is no definitive serologic test for typhoid or paratyphoid fever, the diagnosis often has to be made clinically. Paratyphoid B is diagnosed by the isolation of the agent in blood or stool and demonstration of antibodies anti BH in the Widal test. Antibodies to paratyphoid C are not usually tested and the diagnosis is made with blood cultures.

# Treatment

## Medical Therapy
Empiric treatment in most parts of the world would use a fluoroquinolone, most often ciprofloxacin. However, resistance to fluoroquinolones is highest in the Indian subcontinent and increasing in other areas. Injectable third-generation cephalosporins are often the empiric drug of choice when the possibility of fluoroquinolone resistance is high. Patients treated with an appropriate antibiotic may still require 35 days to defervesce completely, although the height of the fever decreases each day. Patients may actually feel worse when the fever starts to go away. If fever does not subside within 5 days, alternative antimicrobial agents or other foci of infection should be considered. Control requires treatment of antibiotics and vaccines prescribed by a doctor. Major control treatments for Paratyphoid fever include ciprofloxacin for ten days or ceftriaxone/ cefotaxime for 14 days or aziththromycin.
Paratyphoid B responds well to chloramphenicol or co-trimoxazole.
Chloramphenicol therapy is generally effective for Paratyphoid C.

## Primary Prevention
Children and adults should be carefully educated about personal hygiene. This would include careful hand washing after defecation and sexual contact, before preparing or eating food, and especially the sanitary disposal of feces. Food handlers should be educated in personal hygiene prior to handling food or utensils and equipment. Infected individuals should be advised to avoid food preparation.
Those who travel to countries with poor sanitation should receive a typhoid vaccine, which provides protection against typhoid fever but not paratyphoid Infection A, B or C, prior to departure. Sexually active people should be educated about the risks of sexual practices that permit fecal-oral contact.
Owners of tropical fish should ensure scrupulous cleaning of aquariums to eliminate potential S. Paratyphi B organisms.

## Secondary Prevention
Exclusion from work and social activities should be considered for symptomatic, and asymptomatic people who are food handlers, healthcare/daycare staff who are involved in patient care and/ or child care, children attending unsanitary daycare centers, and older children who are unable to implement good standards of personal hygiene. The exclusion applies until two consecutive stool specimens are taken from the infected patient and are reported negative.