Overview
Regression fever is an acute infectious disease caused by regression spirochetes transmitted by insect vectors, clinically characterized by periodic high fever with generalized pain and hepatosplenomegaly, and in severe cases, there may be jaundice and hemorrhagic tendency. According to the different vectors, it can be divided into two types: lice-borne regression fever (epidemic regression fever) and tick-borne regression fever (endemic regression fever).
Questions you may be concerned about
Difference between regression fever and intermittent fever
Return fever and intermittent fever can be differentiated from fever characteristics and common diseases.
1. Fever characteristics:
(1) Regression fever usually occurs when the body temperature rises sharply to above 39°C and then falls abruptly to normal levels after a few days, and this period of hyperthermia and feverlessness each lasts for a number of days and then alternates regularly once.
(2) intermittent fever refers to a sudden rise in body temperature to the peak lasted a few hours, and then quickly reach the normal level, the intermittent period usually lasts one day or several days, fever and fever-free period repeatedly and without obvious regular alternation.
2. Common diseases: regression fever is common in leptospirosis; intermittent fever is common in malaria, lymphoma, acute pyelonephritis and so on.
If fever occurs in daily life, it is recommended to go to a regular hospital to avoid delay.
Causes
Spirochaetes regurgitans belong to the genus Spirochaetes or Borrelia. They are generally categorized according to the species of vector insects. There is only 1 species of tick-borne Leptospira regurgitans, which is called Leptospira regurgitans or Leptospira eubermenschiae. Tick-borne regression spirochetes are named according to the species of the vector insect, the soft-bodied tick, and can be categorized into more than 10 species. The morphology of the two types of regression spirochetes is basically the same, with a length of 10-20 μm, a width of 0.3-0.5 μm, and 3-10 thick and irregular spirals, with sharp ends, active movement, and proliferation by transverse division. Gram staining is negative, and Rachel’s or Giemsa’s stain is purplish or red. Cultivation is more difficult, need to add serum, ascites or rabbit tissue fragments of the broth medium in the micro-oxygenation conditions in order to proliferate, inoculated in the abdominal cavity of young mice or chicken embryo chorionic allantoic membrane easy to reproduce. The wall of S. regurgitans does not contain lipopolysaccharide, but its outer membrane proteins have endotoxin-like activity. The body surface antigen is highly variable. It is sensitive to heat, desiccation, and a variety of chemical disinfectants, but is cold-resistant and can survive for 100 days in a coagulated blood clot at 0 °C. This kind of spirochete contains both specific antigen and non-specific antigen, can be partially common antigen with other microorganisms, so the serum of infected animals can have specific complement binding reaction, can also be positive agglutination reaction with the strain of Aspergillus OXK, but with a lower potency. The spirochete antigen is prone to mutation, and the antigenicity of different strains varies, and the antigenicity of strains isolated from the same patient in different febrile periods also varies.
Symptoms
1. Louse-borne regression fever
The incubation period is 2 to 14 days, with an average of 7 to 8 days. The onset of the disease is mostly acute, with sudden onset of high fever, chills, chills, severe headache and generalized muscle and joint pains. Body temperature reaches more than 40℃ in 1～2 days, most of them are auditory fever, and a few of them are flaccid fever or intermittent fever. Some patients have nausea, vomiting, abdominal pain, diarrhea and other symptoms, but also eye pain, photophobia, cough, rhinorrhea and other symptoms. The face and bulbar conjunctiva are congested, pitting hemorrhagic rash can be seen on the limbs and trunk, and gastrocnemius muscle tenderness is obvious. The respiration and pulse rate increase, and fine wet rales can be heard at the bottom of the lungs. In more than half of the cases, the liver and spleen are enlarged, and jaundice may appear in severe cases. Severe patients may have mental and neurological symptoms and signs, such as confusion, delirium, convulsions and signs of meningeal irritation. After the high fever lasts for 6-7 days, the body temperature drops abruptly, accompanied by profuse sweating, and even emaciation may occur. Later, the patient feels weak and depressed, while other manifestations such as hepatosplenomegaly and jaundice disappear or subside, which is the intermittent period. After 7 to 9 days, the fever recurs and the symptoms reappear, which is called “regression”. Most of the return fever episodes are mild, and the duration of the fever is short. After a few days, the fever subsides again and enters the second intermittent period. The average duration of a cycle is about 2 weeks.
2. Tick-borne return fever
The incubation period is 4-9 days, and the clinical manifestations are similar to those of the tick-borne type, but the symptoms are milder, the fever is irregular, and the number of relapses is more frequent, up to 5-6 times. The tick bite site is mostly purplish red elevated inflammatory reaction with localized lymph node enlargement. Hepatosplenomegaly, jaundice, and neurologic symptoms are less frequent than in the tick-borne form, but the rash is more frequent.
Laboratory examination
1. Pathogen examination
Regression fever spirochetes are generally easy to detect within the peripheral blood of patients during the febrile period. In thin blood smear, it is negative with Gram stain, red or purple with Rachel’s or Giemsa’s stain. Under dark-field microscope, it can be seen to move forward or backward flexibly in a rotational and migratory manner and swing to both sides, and the spirochetes can also be found in bone marrow smears. In patients with neuroleptic spirochetes, cerebrospinal fluid pressure and protein can be elevated, cell count can be increased, and spirochetes can be detected, and sometimes urine precipitation is also positive for spirochetes.
2. Blood and urine routine examination
In patients with tick-borne regression fever, the blood leukocyte count is elevated during the febrile period, between (10-20) × 109/L, and returns to normal during the intervals, with little change in the classification, and the leukocyte count is mostly normal in tick-borne patients; platelets may be reduced, and anemia is obvious in patients with a large number of episodes, but the bleeding and clotting time is normal; and in those with jaundice, the blood bilirubin is elevated. A small amount of protein, cells and tubular pattern can be seen in urine.
3. Serum immunologic examination
Specific antibodies can be detected by immunofluorescent antibody test (IFAT) and protein blotting, etc. If the second potency is 4 times higher, it will help the diagnosis.
Diagnosis
The disease can be diagnosed according to epidemiological data such as endemic areas and seasons and the presence or absence of body lice, history of field work or tick bites in patients with tick-borne regression fever, typical fever pattern alternating with intermittent fever, severe headache, generalized muscular pain, hepatosplenomegaly, and other clinical signs, and the detection of spirochetes in the peripheral blood in conjunction with laboratory tests.
Treatment
“Early detection, early diagnosis, early treatment and localized treatment are the principles of treatment for this disease. Treatment measures include antimicrobial drug treatment and symptomatic treatment.
1. Symptomatic treatment
Anyone with high fever and serious condition should be given symptomatic treatment, and attention should be paid to maintaining water and electrolyte balance. Oral antipyretic and analgesic drugs can be used to relieve severe headache. Nausea and vomiting can be treated with oral or intramuscular diphenhydramine or prochlorperazine. If heart failure occurs, special therapy should be given accordingly. Bed rest and a high-calorie fluid or semi-liquid diet should be given during the febrile period. Adrenocorticotropic hormone can be applied for a short period of time in case of severe toxemia.
2. Antibacterial drug treatment
Antibacterial drugs can eliminate the spirochetes in the body, so the treatment has special effect, tetracycline antibacterial drugs are the most effective drugs, benzylpenicillin, procaine penicillin is also good. Slow absorption of penicillin can not kill the spirochetes in the brain, so the disease may recur after treatment; part of the tick-borne regression fever is not sensitive to penicillin, should not be used. Antibacterial drug treatment must pay close attention to the possible Jarisch-Herxheimer reaction (Jarisch-Herxheimer reaction), the reaction can be fatal in severe cases. This is mainly an anaphylactic shock reaction caused by the release of toxins due to the killing of a large number of spirochetes for a short period of time after the patient receives the first dose of penicillin or other antimicrobial drugs, so the dose of the first antimicrobial drug should not be too large, and can be combined with adrenocorticotropic hormone if necessary. Neoarsphenovanillin is used only in patients with late recurrent tick-type regression fever that is less effective with antimicrobials.
Prevention
Prevention of tick-borne regression fever should be based on isolation of the patient and thorough extermination of ticks. Patients should be kept under observation for 15 days after the fever subsides. Contacts should also be thoroughly exterminated, and if necessary, oral doxycycline should be taken to prevent the onset of disease. Tick-borne regression fever should be eliminated by exterminating ticks and rats. The ticks can be sprayed with malathion or dichlorvos, and the rats can be poisoned with drugs and trapped. Attention should be paid to personal protection when carrying out tasks in infected areas, and oral doxycycline or tetracycline should be taken to prevent morbidity when necessary.