Typhus Fevers

Several distinct Rickettsiae species cause typhus fevers in humans.

Each agent produces disease with a distinct epidemiology, but all cause illness, usually with fever, headache, or rash, or a combination of these.

• Epidemic typhus is passed from person to person by the body louse.
• Endemic, or murine, typhus occurs worldwide and is transmitted by rat fleas.
• Tickborne typhus fevers occur in Europe, Africa, the Americas, Australia, and Asia.
• Scrub typhus, transmitted by rodent mites, occurs in a large area from the Indian subcontinent to Australia and in much of Asia, including, Japan, China, Korea, and parts of Russia.

Occurrence

• Endemic typhus is common year round in the tropics. In temperate areas, it occurs during the summer months when rats and their fleas are most active and abundant.
• Epidemic typhus are rare except during periods when normal hygiene is disrupted, as in refugee camps arising from wars or natural disasters. It also occurs in some populations living in higher elevations during the colder months when louse-infested clothing is not laundered and person-to-person spread of lice is common.
• Scrub typhus can occur throughout the year, but is dependent on temperature and rainfall (which affect the prevalence of the mites that transmit the disease).

Risk for Travelers

• Endemic typhus occurs often in people frequenting rat-infested buildings and houses in harbor areas.
• Epidemic typhus exist in impoverished and dislocated populations in the highlands of some parts of Africa and South America, but travelers are rarely at risk of acquiring lice and disease.
• Scrub typhus and tick typhus occur in people who engage in occupational or recreational behaviors that bring them inadvertently in contact with mite- or tick-infested habitats that harbor the rodent hosts of these arthropods. Tick typhus infections, often called spotted fevers, occur occasionally in travelers who spend time in nature trekking or camping, or on safari.

Preventive Measures

• Vaccine

No commercially licensed vaccines

• Other

Travelers should be advised that prevention is based on avoidance of vector-infested habitats, use of repellents and protective clothing when exposed, prompt detection and removal of arthropods on clothing and skin, and attention to hygiene. Disease management should focus on early detection and proper treatment to prevent severe complications of these illnesses.

Diagnosis - Signs -Symptoms   Treatment

1-Scrub ( chigger –borne) Typhus:        

Scrub typhus is an acute, febrile, infectious illness caused by Rickettsia tsutsugamushi, The term scrub is used because of the type of vegetation (terrain

between woods and clearings) that harbors the vector; however, the name is not entirely correct because certain endemic areas can also be sandy and semiarid.

Pathophysiology: The incubation period from the mite bite is 6-18 days following inoculation.

Humans acquire the disease when an infected mite or chigger, bites them while feeding and inoculates R tsutsugamushi pathogens. The bacteria multiply at the inoculation site with the formation of a papule that ulcerates and becomes necrotic, evolving into an eschar, with regional lymphadenopathy that progresses to generalized lymphadenopathy within a few days. Before symptoms develop, patients are rickettsemic. As in other rickettsial diseases, perivasculitis of the small blood vessels occurs.

Mortality rates in untreated patients range from 0-30%.

(ARDS)–, myocarditis, and disseminated intravascular coagulation (DIC).

Lab Studies:

• Routine laboratory studies reveal early lymphopenia with late lymphocytes.
• Albuminuria is a common laboratory finding.
• Weil-Felix OXK strain agglutination test
• Approximately 50% of patients have a positive test result during the second week of the disease.

     This test is not very sensitive, but it is rather specific, despite having        cross-reactivity in patients with leptospirosis.

• Other tests include the indirect microimmunofluorescent test
• The immunoperoxidase test
• Polymerase chain reaction (PCR).

Medical Care:

Doxycycline –Ciprofloxacin-Tetracycline -. To reduce the risk of relapse, treatment should be administered for at least 14 days.

2- Epidemic ( louse borne) Typhus

Epidemic typhus, is caused by Rickettsia prowazekii, is transmitted in the feces of the infected body louse. Body lice live in clothing and are easily controlled by good personal hygiene.

Louse-infested populations are primarily those who live in extreme poverty. Typhus has been associated with war, famine, refugee camps, cold weather, and conditions that lead to domestic crowding and reduced personal hygiene.

Incubation period: 1 week

Fever +  macular rash leads to maculopapular and petechial rash if not treated.

Photophobia- Skin necrosis- digit gangrene,

Untreated case mortality : 40%

The diagnosis of epidemic typhus was established by demonstrating increasing antibody titers from the acute to the convalescent- phase of illness, with the presence of immunoglobulin (Ig) M to R. prowazekii

The diagnosis was confirmed by the isolation of R. prowazekii in blood – IFA testing.

Treatment: Doxycycline

3- Endemic  ( murine ) Typhus ( flea borne) :

• Cause by Rickettsia typhi, transmitted rats fleas feces that are scratched into pruritic  bite lesions or inhaled

• Incubation: 11 days.
• Duration of untreated illness =12 days
• Symptoms: Headache-myalgia-nausea-malaise-chills – fever-macular rash –
• Pulmonary: cough- pneumonia-
• Complication: bleeding disorder- cerebral bleeding-renal failure

Diagnosis: IFA – PCR- Elisa testing.

Treatment  : Doxycycline

4-Tick typhus (Rocky Mountain spotted fever + Spotted Fever; Tick Fever)

 (RMSF) is limited to the Western Hemisphere. Hard-shelled ticks (family Ixodidae) harbor R. rickettsii

Small blood vessels are the sites of the characteristic pathologic lesion. Rickettsiae propagate within damaged endothelial cells, and vessels may become blocked by thrombi, producing vasculitis in the skin, subcutaneous tissues, CNS, lungs, heart, kidneys, liver, and spleen. Disseminated intravascular coagulation often occurs in severely ill patients

Symptoms and Signs

The incubation period averages 7 days but varies from 3 to 12 days;

Onset is abrupt, with severe headache, chills, prostration, and muscular pains. Fever reaches 39.5 or 40° C (103 or 104° F) within several days and remains high (for 15 to 20 days in severe cases). Between the 1st and 6th day of fever, most patients develop a rash on the wrists, ankles, palms, soles, and forearms that rapidly extends to the neck, face, axilla, buttocks, and trunk.

Hepatomegaly may be present, but jaundice is infrequent. Localized pneumonitis may occur. Untreated patients may develop pneumonia, tissue necrosis, and circulatory failure, with such sequelae as brain and heart damage. Cardiac arrest with sudden death occasionally occurs in fulminant cases.

Prognosis ,Prophylaxis and treatment

Starting antibiotics early has significantly reduced mortality from about 20 to 7%. Early treatment prevents most complications.

No effective vaccines are available.

Preventing tick access to skin includes tucking trousers into boots or socks, wearing long-sleeved shirts, and applying repellents with 25 to 40% diethyltoluamide (deet) to skin surfaces. Permethrin on clothing effectively repels ticks.

 Engorged ticks should be removed with care and not crushed between the fingers because of the danger of transmission. Gradual traction of the head with a small forceps dislodges the tick. The point of attachment should be swabbed with alcohol.

Antibiotics : Doxycycline