Paratyphoid fever, which is sometimes called Salmonella paratyphi infection, is a serious contagious disease caused by a gram-negative bacterium. It is also grouped together with typhoid fever under the name enteric fever.
Paratyphoid fever has three stages: an early stage marked by high fever; a toxic stage with abdominal pain and intestinal symptoms, and a long period of recovery from fever (defervescence). In adults, these three phases may cover a period of four to six weeks; in children, they are shorter and may cover 10 days to two weeks. During the toxic stage there is a 1-10% chance of intestinal perforation or hemorrhage.
Causes and symptoms
Paratyphoid fever is caused by any of three strains of Salmonella paratyphi: S. paratyphi A; S. schottmuelleri (also called S. paratyphi C ); or S. hirschfeldii (also called S. paratyphi B ). It can be transmitted from animals or animal products to humans or from person to person. The incubation period is one to two weeks but is often shorter in children. Symptom onset may be gradual in adults but is often sudden in children.
Paratyphoid fever is marked by high fever, headache, loss of appetite, vomiting, and constipation or diarrhea. The patient typically develops an enlarged spleen. About 30% of patients have rose spots on the front of the chest during the first week of illness. The rose spots develop into small hemorrhages that may be hard to see in African or Native Americans.
Patients with intestinal complications have symptoms resembling those of appendicitis: intense cramping pain with soreness in the right lower quadrant of the abdomen.
The diagnosis is usually made on the basis of a history of recent travel and culturing the paratyphoid organism. Because the disease is unusual in the United States, the doctor may not consider paratyphoid in the diagnosis unless the patient has the classic symptoms of an enlarged spleen and rose spots. The doctor will need to rule out other diseases with high fevers, including typhus, brucellosis, tularemia (rabbit fever), psittacosis (parrot fever ), mononucleosis, and Kawasaki syndrome. S. paratyphi is easily cultured from samples of blood, stool, urine, or bone marrow.
Paratyphoid fever is treated with antibiotics over a two- to three-week period with trimethoprimsulfamethoxazole (Bactrim, Septra); amoxicillin (Amoxil, Novamoxin); and ampicillin (Amcill). Thirdgeneration cephalosporins (ceftriaxone [Rocephin], cefotaxime [Claforan], or cefixime [Suprax]) or chloramphenicol (Chloromycetin) may be given if the specific strain is resistant to other antibiotics.
Patients with intestinal perforation or hemorrhage may need surgery if the infection cannot be controlled by antibiotics.
Patients with paratyphoid fever need careful monitoring for signs of complications as well as bed rest and nutritional support. Patients with severe infections may require fluid replacement or blood transfusions.
Most patients with paratyphoid fever recover completely, although intestinal complications can result in death. With early treatment, the mortality rate is less than 1%.
Vaccination against paratyphoid fever is not necessary within the United States but is recommended for travel to countries with high rates of enteric fever.
Travelers in countries with high rates of paratyphoid fever should be careful to wash hands before eating and to avoid meat, egg, or poultry dishes unless they have been thoroughly cooked.
Defervescence— Return to normal body temperature after high fever.
Enteric fever— A term that is sometimes used for either typhoid or paratyphoid fever.
Rose spots— Small slightly raised reddish pimples that are a distinguishing feature of typhoid or paratyphoid infection.
Fauci, Anthony S., et al., editors. Harrison's Principles of Internal Medicine. New York: McGraw-Hill, 1997.