Cd alert

Monthly Newsletter of National Centre for Disease Control,
Directorate General of Health Services, Government of India
May - July 2009
Vol. 13 : No. 1
SCRUB TYPHUS & OTHER RICKETTSIOSES
it lacks lipopolysaccharide and peptidoglycan RICKETTSIAL DISEASES
and does not have an outer slime layer. It is These are the diseases caused by rickettsiae endowed with a major surface protein (56kDa) which are small, gram negative bacilli adapted and some minor surface protein (110, 80, 46, to obligate intracellular parasitism, and considerable differences in virulence and organisms are primarily parasites of arthropods antigen composition among individual strains such as lice, fleas, ticks and mites, in which they are found in the alimentary canal. In vertebrates, including humans, they infect the vascular endothelium and reticuloendothelial GLOBAL SCENARIO
cells. Commonly known rickettsial disease isScrub Typhus.
Geographic distribution of the disease occurswithin an area of about 13 million km2 including- The family Rickettsiaeceae currently comprises Afghanistan and Pakistan to the west; Russia of three genera – Rickettsia, Orientia and to the north; Korea and Japan to the northeast; Indonesia, Papua New Guinea, and northern of the family, Coxiella burnetii, which causes first observed in Japan where it was found to trench fever have been excluded because the be transmitted by mites. The disease was, former is not primarily arthropod borne and therefore, called tsutsugamushi (from tsutsuga the latter is not an obligate intracellular parasite, being capable of growing in cell-free media, insect or mite). This is found only in areas besides being different in genetic properties.
with a suitable climate, plenty of moisture and Scrub typhus will be dealt in detail.
scrub vegetation. Recently, rickettsioses has SCRUB TYPHUS
been an emerging disease along the ThaiMyanmar border. There are reports of CAUSATIVE AGENT
emergence of scrub typhus in Maldive Islandsand Micronesia.
Scrub typhus (Chigger borne typhus,Tsutsugamushi fever) is caused by Orientia INDIAN SCENARIO
tsutsugamushi. Orientia is a small (0.3 to 0.5by 0.8 to 1.5 µm), gram negative bacterium of In India, scrub typhus has been reported from the family Rickettsiaceae. It differs from the Rajasthan, Jammu & Kashmir and Vellore. In other members in its genetic make up and in addition, few cases have been tested positive the composition of its cell wall structure since for IgM antibodies for scrub typus from Sikkim, Darjeeling, Nagaland & Manipur (unpublished morning, chiggers can be collected from the data). In a study conducted from July through body of the sentinel animals. The mites can be preserved in 70% alcohol till they reach cases of acute febrile illness of unknown origin, laboratory for identification. Chigger index O.tsutsugamushi was identified as causative (average number of chiggers infesting a single agent by microimmunofluorescence and PCR.
host) of > 0.69 (critical value) is an indicator In an entomolgic study in Himachal Pradesh, for implementation of vector control measures.
vector species Leptotombidium deliense andGahrliepia spp. were recorded.
Habitats favorable for disease transmission
Scrub typhus, originally found in scrub jungles, DISEASE TRANSMISSION
Leptotrombidium deliense. The vector mites mountain deserts and equatorial rain forests.
inhabit sharply demarcated areas in the soil Incubation Period
where the microecosystem is favourable (miteislands). Human beings are infected when they trespass into these mite islands and are bittenby the mite larvae (chiggers). The mite feeds CLINICAL PICTURE
on the serum of warm blooded animals onlyonce during its cycle of development, and adult A Papule develops at the site of inoculation.
mites do not feed on man. The microbes are The papule ulcerates and eventually heals transmitted transovarially in mites. Scrub mammals, particularly field mice and rodents.
(>40ºC [104ºF]) with relative bradycardia, The L.deliense group of vector mites are widely distributed all over the country coexisting Approximately one week later, a spotted and hosts, the chiggers attach in clusters on the tragus of the ear, the belly and on the thighs.
the trunk and then on the extremities and The Leptotrombidium mites, on the rat host, may appear orange or pink. The typical vector L.deliense is generally found associated with (30 to 65% of cases), meningoencephalitis secondary vegetation after clearance of forestareas. This species is generally abundant on grasses and herbs where bushes are scarce.
Sentinel animals can also be used for collection of trombiculid mites from the field. These myocarditis, the mortality rate may reach animals are generally white laboratory mice or rats kept in small cages containing food andwater and placed in the field overnight to attract DIAGNOSIS
chiggers. Chiggers can also be collected fromfield directly on human beings, by walking in Routine laboratory tests are unlikely to be the field after wearing stockings. The following diagnostic for any rickettsial diseases.
Common clinical manifestations of the Rickettsial Diseases
Scrub Typhus axillary eschar
Maculopapular rash on back of
a case of scub typhus
Laboratory diagnosis
early lymphopenia with late lymphocytosis.
Scrub typhus may be diagnosed in the laboratory finding. Thrombocytopenia is observed in more Collection, storage & transportation of
specimen
all pertinent information to laboratory whichwill help in better interpretation of the The collection, transportation and storage of specimens are extremely vital steps in laboratorydiagnosis and hence, must be undertaken with Isolation of the organism
As rickettsiae are highly infectious and have Specimen
caused several serious and fatal infectionsamong laboratory workers, it comes under Risk Group 3 organisms. Isolation should be done in laboratories equipped with appropriate safety provisions preferably Biosafety level-3 labora-tory following strict biosafety precautions.
Rickettsia may be isolated in male guinea pigs Blood collection in tubes and vials
or mice; yolk sac of chick embryos; vero cellline or MRC 5 cell lines from patients in early Aseptically collect 4-5 ml of venous blood.
phase of the disease. Egg and animal inocula- tion methods have been replaced by faster and centrifuge at 2000 rpm to separate serum.
more sensitive cell cultures. Rickettsiae growwell in 3-5 days on Vero cell and MRC 5 cell Collect the serum in sterile dry vial.
coverslip cultures and can be identified by im-munofluorescence using group and strain spe- Fix the cap with adhesive tape, wax or other sealing material to prevent leakage duringtransport.
Serological diagnosis
Diagnosis of the etiology of rickettsial diseases indelible ink, or a typewritten self adhesive can be accomplished most easily and rapidly label to identify the container. The name of by demonstrating a significant increase in anti- the patient, identification number and date of bodies in the serum of the patient during the collection must be indicated on the label.
course of infection and convalescence. Severalserological tests are currently available for the Do’s/Don’ts while collecting specimen:
diagnosis of rickettsial diseases like Weil-Felix Test (WFT), Indirect Immunoflourescence (IIF),Enzyme linked Immunosorbent assay (ELISA) etc. Although many techniques have been used successfully for rickettsial sero diagnosis, rela-tively few are used regularly by most laborato- ries. BSL-3 Lab is not required for performing laboratory at 2-8ºC (ice box) as soon as Weil-Felix Test (commonly used test)
Don’t freeze whole blood as haemolysismay interfere with serology test results.
The Weil-Felix test is helpful in establishingpresumptive diagnosis in diseases caused by In case the delay is inevitable, keep the members of typhus and spotted fever groups of specimen at + 4ºC in a refrigerator.
Rickettsiae. The interpretation of Weil-Felix test Molecular diagnosis – PCR
Table 1 : Weil-Felix Test
For PCR, blood sample is collected in tubescontaining EDTA or sodium citrate. However, blood clot, whole blood or serum can also beused for the detection of O.tsutsugamushi, R.rickettsii, R. typhi and R.prowazekii organismsby PCR test.
Facilities for laboratory diagnosis of Rickettsial diseases are available at National Centre forDisease Control, Delhi where samples can be TREATMENT
Prompt institution of effective antibiotic therapy against rickettsiae is the single most effectivemeasure for preventing morbidity and mortality due to rickettsial diseases. Anti rickettsial therapyimproves the outcome of all rickettsioses, with The sensitivity and specificity of the Weil-Felix test is reported to be low as compared to the complicated cases of RMSF, epidemic typhus specific serological tests for detection of IgM and scrub typhus where the illness is no longer antibodies. However, comparative evaluation of susceptible to intervention. If the illness is severe, Weil-Felix test and IgM ELISA for diagnosis of the cardiac, pulmonary, renal, and central Scrub Typhus carriedout at NCDC, showed that Weil Felix test is equally sensitive with specific- additional measures instituted to prevent Indirect Immunofluorescent antibody (IFA)
Tetracyclines and chloramphenicol remain the only proven therapy for the rickettsial diseases.
Doxycycline in a dose of 100 mg twice daily for IFA is used as a reference technique; however, availability and cost are major constraints and times a day PO for 7-15 days (for children 150 is not available in most of the laboratories.
mg/kg/day for 5 days) is recommended.
Enzyme linked Immunosorbent Assay
Tetracyclines may cause discoloration of teeth, hypoplasia of the enamel, and depression ofskeletal growth in children; the extent of ELISA techniques, particularly immunoglobulin discolouration is directly related to the number M (IgM) capture assays, are probably the most of courses of tetracycline therapy received.
sensitive tests available for rickettsial diagnosis, Therefore, tetracycline should not be used for and the presence of IgM antibodies, indicate children under 8 years of age and for pregnant recent infection with rickettsial diseases. In cases of infecton with O.tsutsugamushi, asignificant IgM antibody titer is observed at the PREVENTION AND CONTROL
end of the first week, whereas IgG antibodies The mite vectors of scrub typhus are especially appear at the end of the second week.
amenable to control because they are often found in distinct areas (Typhus Island).
infection but not the pubic louse. The licebecome infected by feeding on rickettsiaemic patients. The rickettsiae multiply in the gut of the lice and appear in the faeces in 3-5 days.
insecticides, reducing rodent populations, Lice succumb to the infection within 2-4 weeks, remaining infective till they die. They can transmit the infection after about a week of being infected.
Persons who cannot avoid infested terrain Transmission
should wear protective clothing, impregnatetheir clothing and bedding with a mitecide (e.g.
Lice may be transferred from person to person.
benzyl benzoate) and apply a mite repellent, Being sensitive to temperature changes in the host, they leave the febrile patient or the cooling carcass and parasitise other persons. Lice defecate while feeding. Infection is transmittedwhen the contaminated louse faces is rubbed by scratching. Occasionally, infection may also decreased the incidence of clinical illnesses be transmitted by aerosols of dried louse faces through inhalation or through the conjunctiva.
Incubation period: 5 - 15 days.
been developed till now, mainly due toserotypic heterogeneity of the organism.
Clinical Presentation
OTHER RICKETTSIAE INFECTIONS
The disease starts with fever and chills.
EPIDEMIC TYPHUS
A characteristic rash appears on the fourthor fifth day, starting on the trunk and spreading Epidemic typhus (Louseborne typhus, Classical over the limbs but sparing the face, palms typhus, Gaol fever) has been one of the great scourges of mankind, occurring in devastating epidemics during times of war and famine. The disease has been reported from all parts of the world but has been particularly common in of consciousness in the disease. The case Russia and Eastern Europe. During 1917-1922, fatality may reach 40% and increases with there were some 25 million cases in Russia, with about three million deaths. In recent times,the main foci have been Eastern Europe, Africa, In some who recover from the disease, the South America and Asia. In India, the endemic rickettsiae may remain latent in the lymphoid tissues or organs for years. Such latent infectionmay, at times, be reactivated leading to The causative agent of epidemic typhus is recrudescent typhus or Brill Zinsser disease.
R.prowazekii, named after von Prowazek.
Brill noticed a mild, sporadic, typhus-like disease Humans are the only natural vertebrate hosts.
Natural infection in flying squirrels has been reported from South- eastern USA. The human R.prowazekii from such cases and proved that body louse, Pediculus humanus corporis, is the vector. The head louse may also transmit the ENDEMIC TY\PHUS
Endemic typhus (Murine typhus) is a milderdisease than epidemic typhus. It is caused byR.typhi which is maintained in nature as a mildinfection of rats, transmitted by the rat flea,Xenopsylla cheopis. The rickettsia multiplies inthe gut of the flea and is shed in its faeces. Theflea is unaffected but remains infectious for therest of its natural span of life. Humans acquirethe disease usually through the bite of infectedfleas, when their saliva or faeces is rubbed in orthrough aerosols of dried faeces. Ingestion of Eschar of tick bite over the left side of the abdomen
food recently contaminated with infected rat urineor flea faeces may also cause infection. Human a case of endemic typhus or with a culture of infection is a dead end. Man to man transmission R.typhi, they develop fever and a characteristic does not occur. In India, endemic typhus has
scrotal inflammation. The scrotum becomes been reported from Pune, Lucknow,
enlarged and the testes cannot be pushed back Mysore, Kolkata, Golkunda, Karnal, Rewari
and Kashmir.
adhesions between the layers of the tunicavaginalis. This is known as the Neil-Mooser or Clinical presentation
the tunica reaction. The Neil-Mooser reaction is SPOTTED FEVER GROUP
They are all transmitted by ticks, except R.akari, headache, fever and rash. This is seen only which is mite borne. Rickettsiae of this group possess a common soluble antigen and multiplyin the nucleus as well as in the cytoplasm of Rash develops in 54% of patients some time host cells. Many species have been recognized Nausea, vomiting, diarrhoea and abdominalpain suggest gastrointestinal diseases while Organism
cough and abnormal chest radiographsuggests pneumonia or bronchitis.
renal insufficiency and respiratory failureare seen in approximately 10% of cases, R.typhi and R.prowazekii are closely similar but may be differentiated by biological andimmunological tests. When male guinea pigs are inoculated intraperiotoneally with blood from The rickettsiae are transmitted transovarially in ticks, which therefore act as both vectors and reservoirs. The infection may be transmitted to vertebrate hosts by any of the larval stages or by adult ticks. Ticks are not harmed by the sanguineus is the most important vector and is rickettsiae and remain infected for life. The generally found infesting dogs all over.
transmission to human beings is primarily by Hyalomma ticks may also transmit the infection.
bite, as the rickettsiae also invade thesalivary glands of the ticks. All rickettsiae of this The incubation period ranges from 2 to 7 days.
group pass through natural cycles in domestic In >50% of the patients, a primary lesion with central necrosis (eschar) appears at the site ofthe tick bite. The lesion is covered with a brownish ROCKY MOUNTAIN SPOTTED FEVER
black scab (tachy noire) and may ulcerate.
Recall of a tick bite cannot always be elicited Rocky Mountain Spotted Fever (RMSF) is the from the patient. Regional lymphandenitis is most serious type of spotted fever and is the common. The fever lasts for 1 to 2 weeks and first to have been described. It is prevalent in many parts of North and South America and is myalgias and a generalized maculopapular rash which develops between the third and fifth days of illness or which may not appear. It disappears TICK TYPHUS (INDIAN TICK TYPHUS)
at the time of defervescence. Alterations incytokine profiles, hypercoagulability and deep Tick typhus, in several parts of Europe, Africa venous thrombosis may occur. In severe cases and Asia is caused by R.conori, strains of which – particularly in elderly patients and those with isolated from the Mediterranean region, Kenya, diabetes mellitus, alcoholism or heart failure – South Africa and India are indistinguishable. The meningoencephalitis with coma and seizures species is named after Conor, who provided the and/or disseminated vasculitis of internal organs first description of the Mediterranean disease.
(e.g. in the heart, lungs, kidneys, liver and Tick typhus was first observed in India in the pancreas) are observed. The mortality rate is 1 foothills of the Himalayas. Subsequently, the to 5% but is higher among patients with severe disease was reported from many parts of the .about CD Alert
CDAlert is a monthly newsletter of the National Centre for Disease Control (NCDC) (formerly known as NICD), Directorate
General of Health Services, to disseminate information on various aspects of communicable diseases to medical fraternity and health administrators. The newsletter may be reproduced, in part or whole, for educational purposes.
Dr. Shiv Lal, Dr. R. L. Ichhpujani, Dr. Shashi Khare, Dr. A. K. Harit Dr. D. Bhattacharya, Dr. Veena Mittal, Dr. Naveen Gupta, Dr. A.C. Dhariwal, Dr. Arti Bahl Director, National Centre for Disease Control, 22 Shamnath Marg, Delhi 110 054 Tel: 011-23971272, 23971060 Fax : 011-23922677 E-mail: [email protected] and [email protected] Website: www.nicd.nic.in Financial assistance by WHO/USAID is duly acknowledged.
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