Archive for September, 2008

Typhus: Endemic Murine Typhus

Endemic murine typhus is caused by Rickettsia typhi. R. typhi is maintained in mammalian host-flea cycles, with rats (Rattus rattus and R. norvegicus) and the Oriental rat flea (Xenopsylla cheopis). Fleas get R. typhi from rickettsemic rats and carry the organism throughout their life. Humans are infected when rickettsia-laden flea feces contaminate itchy bite lesions. Rats are infected if they are not immune to R. typhi. The flea bite can also transmit the organisms, but much less frequently. Transmission can occur via inhalation of aerosolized rickettsiae from flea feces. Rats are rickettsemic for about 2 weeks, though they appear healthy.

Epidemiology: endemic typhus occurs year-round, in warm (often coastal) areas throughout the tropics and subtropics, where it is highly prevalent. In USA Murine typhus occurs mainly in southern Texas and southern California. The classic rat-flea cycle is absent and an opossum-cat flea (C. felis) cycle is prominent in USA.

Symptoms & signs: The incubation period typhus is 8–16 days. Headache, arthralgia, myalgia, nausea, and malaise develop 1–3 days before onset of chills and fever. Nausea and vomiting is very common. The duration of untreated illness ranges from 9–18 days. Rash is present in some patients in axilla or the inner surface of the arm.

About one third of the patients have respiratory problems like a hacking, nonproductive cough, pulmonary edema, and pleural effusions. Abdominal pain, confusion, stupor, seizures, ataxia, coma, and jaundice can be seen less frequently.

Diagnosis: Diagnosis is mainly by clinical symptoms. Cultivation and PCR in acute and convalescent-phase sera can provide a specific diagnosis of endemic murine typhus.

Treatment: Doxycycline 100 mg twice orally for 7–15 days on the basis of clinical suspicion is the treatment of choice.

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Posted by - September 30, 2008 at 1:07 pm

Categories: Ricketssial Diseases   Tags: , ,

Q Fever (Chronic): Treatment

Symptoms: Chronic Q fever usually occurs in patients with previous valvular heart disease, chronic renal insufficiency, or immunosuppression. Chronic Q fever generally implies endocarditis. Fever is generally low grade or absent. The disease should be suspected in all patients with culture-negative endocarditis.

Epidemiology: The primary sources of human infection are infected sheep, cattle, camel and goats. But cats, dogs, rabbits, and pigeons also can transmit C. burnetii to humans and cause Q fever. The wild reservoir includes ticks. In the infected animals C. burnetii localizes to the uterus and the mammary glands and is activated during pregnancy. C. burnetii is concentrated in the placenta and at the time of parturition (delivery), C. burnetii organisms are released into the air, and infection follows inhalation of aerosolized organisms by a susceptible host. So, C. burnetii can be a potential agent of bioterrorism.

Veterinarians, abattoir workers and other individuals who have contact with infected animals, mainly newborn animals or products of conception are at great risk of getting Q fever. C. burnetii is found in milk for weeks to months after parturition and ingestion of contaminated milk in some areas can be a major route of transmission to humans. But the vast majority of Q fever cases result from inhalation of contaminated aerosols.

Q fever can occur throughout the world except New Zealand and Antarctica.

Treatment: The treatment of chronic Q fever is very difficult and needs careful follow-up. Preferred regimen of treatment of chronic Q fever is doxycycline (100 mg twice a day) and hydroxychloroquine (200 mg thrice a day; plasma concentration maintained at 0.8–1.2 µg/ml) for 18 months. This is better than a regimen of doxycycline and ofloxacin. Q fever endocarditis requires determination of the minimal inhibitory concentration (MIC) of doxycycline for the patient’s isolate of C. burnetii and measurement of serum doxycycline levels. The doxycycline-hydroxychloroquine regimen is successful in patient with HIV infection and Q fever endocarditis. If doxycycline-hydroxychloroquine cannot be used, than at least two antibiotics active against C. burnetii like Rifampin (300 mg once daily) combined with doxycycline (100 mg twice daily) or ciprofloxacin (750 mg twice daily) should be used.

Treatment of C. burnetii infected aortic aneurysms is the same as that for Q fever endocarditis but surgical intervention is frequently required.

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Posted by - September 29, 2008 at 3:08 pm

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Q Fever (Acute): Treatment

The incubation period of Q fever is 3–30 days. The symptoms are nonspecific and mainly consist of fever, extreme fatigue, and severe headache. Chills, sweats, nausea, vomiting, and diarrhea may also occur. Cough is seen if patient develops Q fever pneumonia. Thrombocytopenia occurs in about 25% of patients, and reactive thrombocytosis with platelet counts sometimes exceeding 106/µL can develop during recovery.

Acute Q fever can complicate pregnancy and cause premature birth, abortion or neonatal death. Q fever in children is generally asymptomatic. Some cases of Q fever can lead to endocarditis (Q fever endocarditis).

Diagnosis: Diagnosis is by serology. Indirect immunofluorescence is sensitive and specific and is the method of choice for diagnosis. PCR (polymerase chain reaction) detects C. burnetii DNA in tissues.

Treatment of Q fever: Treatment of choice in acute Q fever is doxycycline 100 mgs twice a day for two weeks (14 days). Quinolones like ciprofloxacin, ofloxacin and gatifloxacin are also successful. Treatment of Q fever in pregnancy is with trimethoprim-sulfamethoxazole.

Prevention: A whole-cell vaccine (Q-Vax) is licensed in Australia and effectively prevents Q fever in abattoir (slaughterhouse) workers. Skin testing with intradermal diluted C. burnetii vaccine is done before administering vaccine. A history of possible Q fever is sought and vaccine is given only to patients with no history of Q fever and negative results in serologic and skin tests.

Good animal-husbandry practice is very important to prevent contamination of environment by C. burnetii. Only seronegative animals should be permitted in zoos.

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Posted by - September 28, 2008 at 5:56 am

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Mediterranean Spotted Fever: Treatment

Mediterranean Spotted Fever also known as Boutonneuse Fever. It is caused by   Rickettsia conorii. It is prevalent in southern Europe, Africa, and southwestern and south-central Asia. Regional names for the disease caused by this organism include Mediterranean spotted fever, Indian tick typhus, Israeli spotted fever, Kenya tick typhus, and Astrakhan spotted fever.

 The symptoms include headache, fever, eschar(tache noire), and regional lymphadenopathy. It is characterized by high fever, rash, and an inoculation eschar at the site of the tick bite. In patients with diabetes, alcoholism, or heart failure the disease can be very severe and mortality is as high as 50% in these patients.

Mediterranean Spotted Fever is diagnosed mainly by clinical findings in the areas where it is endemic and is confirmed by serology, immunohistochemical demonstration of rickettsia in skin biopsy and cell culture & isolation of rickettsia.

  Treatment: The drug of choice for the treatment of Mediterranean Spotted Fever is doxycycline and ciprofloxacin. Doxycycline is given 100 mg orally two times a day for 1-5 days depending on severity. Ciprofloxacin is given 750 mg orally two times a day for 5 days. Other drug which can be used is chloramphenicol 500 mg orally four times per day for 7-10 days.

In mildly ill children clarithromycin or azithromycin can be used successfully. But these are not very successful for treatment of adults. These two drugs are also not useful in severely ill pediatric patients.

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Posted by - September 27, 2008 at 1:07 pm

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Rocky Mountain Spotted Fever: Treatment

Rocky Mountain Spotted Fever (RMSF) is the most severe of all rickettsial diseases. RMSF is caused by Rickettsia Rickettsii. It is characterized by fever, headache, malaise, myalgia (muscle pain), nausea, vomiting, and anorexia for first three days. The patient becomes progressively ill.

RMSFoccurs in all 48 adjoining states in USA (highest prevalence in the south-central and southeastern states) and also in Canada, Mexico, and Central and South America. The infection is transmitted by Dermacentor  andersoni, the Rocky Mountain wood tick, in the western United States and by D. variabilis, the American dog tick, in the eastern two-thirds of the United States and California. It is transmitted by Rhipicephalus sanguineus in Mexico and by Amblyomma cajennense in Central and South America.

Humans usually become infected during tick season (from May to September in the Northern Hemisphere).

Treatment: The drug of choice for the treatment of both adults and children with RMSF is doxycycline except when the patient is allergic to this drug or pregnant. Rocky Mountain Spotted Fever Is very severe disease and prompt treatment with empirical administration of doxycycline should be given as soon as it is diagnosed or suspected strongly. Doxycycline is administered orally at 200 mg/d in two divided doses, in the presence of coma or vomiting, it is given intravenously. For children, up to five courses of doxycycline may be administered with minimal risk of dental staining.

Other drugs include oral tetracycline (25–50 mg/kg per day) in four divided doses. Chloramphenicol can be given if patients are pregnant or allergic to doxycycline.

The antirickettsial drug should be given till the patient has been afebrile (without fever) and improving clinically for 2–3 days. ?-Lactam antibiotics like penicillin, erythromycin, and aminoglycosides have no role in the treatment of RMSF, and sulfa-containing drugs can aggravate this infection.

Prevention of RMSF: tick bites should be avoided as much as possible (although it is not very practicable). Protective clothing and tick repellents can be used; inspection of the body once or twice a day, and removal of ticks before they inoculate rickettsiae reduce the risk of infection. There is no vaccine available for RMSF.

 

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Posted by - September 26, 2008 at 3:22 pm

Categories: Ricketssial Diseases   Tags: , , ,