Rickettsial Disease Management
Megha G.K 1 and Shikha Tamta2
1Ph. D Scholar, Department of Veterinary Public Health and Epidemiology
ICAR- Indian Veterinary Research Institute, Izzatnagar, Bareilly, U.P. India
2Assistant Professor, Department of Veterinary Public Health and Epidemiology, International Institute of Veterinary Education and Research, Rohtak, Haryana,124001, India
Introduction
The genus Rickettsia includes Gram-negative, non-spore-forming, non-motile, tiny, obligate, I/C extremely pleomorphic bacteria that can take the shape of cocci, bacilli, or threads. analogous to Gram-negative bacteria outer membrane, peptidoglycan, and lipopolysaccharide make up the cell wall (LPS) a polysaccharide and a microcapsule, two groups, each antigenically unique: According to the Weil-Felix test, LPS is heat-stable and reacts with somatic antigens from non-motile Proteus species. The outer membrane protein, however, is heat-unstable and species-specific. Human illnesses are caused by five genera in this class: Bartonella (NOT an I/C organism), Coxiella, Ehrlichia, Orientia, Rickettsia (does NOT cause skin rash &does NOT need arthropod vector). Instead, the bacterium genus Rickettsia bears Howard Taylor Ricketts’ name in recognition of his ground-breaking research on tick-borne spotted fever. They possess an ATP transport mechanism that enables them to use host ATP, allowing them to replicate within the cytoplasm of eukaryotic host cells. Hans Zinsser, a physician and researcher at Harvard Medical School, examined the consequences of illness spread by rodents on armies, towns, and people in 1935. Zinsser concluded definitively from his thorough research on head and body lice that “the body and head louse convey the sickness [typhus] from one individual to the other. Europe saw typhus epidemics from the 17th through the 19th century. The illness claimed three million lives in Russia during World War I, and even more in Poland and Romania. Later epidemics were avoided due to the discovery of DDT. Because DDT is efficient against the mosquito that transmits malaria and the lice that transmit typhus, its usage expanded significantly after World War II. The characteristics of parasites on ticks, fleas, and lice Mites that populate the gut also colonize the vascular endothelium and RES in vertebrates. In the spotted fever group (SFG) of the genus Rickettsia, eight tick-borne species or subspecies have been identified as emerging diseases in Southern and Eastern Europe. Therefore, Rickettsia species must be produced in tissue or embryo cultures instead of artificial nutrient cultures; commonly, chicken embryos are utilized. Numerous Rickettsia infect solely arthropods, frequently non-hematophagous insects like aphids or whiteflies, and are not dangerous to vertebrates, including humans. Since many Rickettsia species are therefore arthropod-specific symbionts, they are frequently mistaken for harmful Rickettsia, especially in medical literature, demonstrating the strong anthropocentric bias of the prevailing perspective in rickettsiology.
Vector responsible for the Rickettsial disease
Only a small portion of the biology of rickettsial disease vectors is understood. The least effective rickettsial host is the human body louse vector of R. prowazekii; all infected lice are destroyed by the rickettsiae. Similar to R. rickettsii, R. africae and R. amblyommatis have high carriage rates in their tick vectors but far lower carriage rates of R. rickettsii, the most dangerous organism, which is detected in less than 0.1% of its vector ticks. Ticks in their adult and nymphal stages can eat for more than a week without being seen. Vector biology of Dermacentor, Amblyomma, and Rhipicephalus ticks represents a gap in knowledge that is relevant to the transmission of Rickettsia species, including phenomena such as reactivation of rickettsial virulence from organisms in unfed ticks that do not cause disease, but are reactivated to virulence during tick feeding.
Transmission and Risk Factors for Exposure
Different tick families are responsible for transmitting the various rickettsial illnesses. Bites from hard body (ixodid) ticks cause the spotted fever group, anaplasmas, ehrlichias, and other diseases. In contrast to R. typhi, which is spread by inadvertent mucosal or parenteral inoculation of rat fleas, R. prowazekii is spread through the biting of infected body lice (Pediculous humanus humanus) or ectoparasites from infected flying squirrels (Xenopsylla cheopsis). Exposure to woodland or brushy environments with tall grasses or bushes during work or play. By not using the recommended tick repellents will lead to extension of the disease. Wearing inappropriate attire in high-risk locations, international travel, exposure to animals and birds (wild, domestic, and/or peridomestic).
Treatment, Prevention and Control
doxycycline or chloramphenicol are the drug of choice for Rickettsiosis. doxycycline is preferred over chloramphenicol. The preferred medication is doxycycline/tetracycline. All patients with suspected rickettsial disease should receive this antibiotic, despite the fact that tetracyclines are typically contraindicated for pregnant women and young children. This is because it is the most effective antibiotic and poorly treated disease is linked to a high morbidity and mortality rate. R. rickettsii can be successfully treated with fluoroquinolones like ciprofloxacin. The strongest defences against R. rickettsii infection are wearing protective clothes, using insect repellents, avoiding tick-infested regions, practising good personal hygiene, and removing attached ticks as soon as possible. There is no vaccination for Rocky Mountain spotted fever.
Preventing tick bites can reduce the chance of illness. In tick ecosystems, protective footwear, attire, and insect repellents should be used. In certain cases, light-coloured clothes make ticks easier to see. Ticks should be removed as quickly as possible using fine-tipped tweezers or gloved hands by those who enter tick habitats. Because numerous tick-transmitted disease organisms can enter the body through wounds in the skin or mucous membranes, bare hands should not be used to remove ticks owing to the potential of exposure to the tick’s fluids or excrement. If gloves are not available, tissues or paper towels should be used to cover the fingers. The tick must not be pinched, pressed, or pierced. The Centers for Disease Control and Prevention (CDC) issues a warning that tick removal methods such using hot matches or petroleum jelly may cause the tick to emit more saliva and raise the risk of infection. After removing the tick, tick bites should be properly cleaned, and hands should be cleansed with soap and water. For identification in the event of an infection, the tick can be frozen in a plastic bag. Additionally, ticks on animals should be removed to protect canines from illness and to keep ticks out of the house. Acaricides, biological controls, and habitat management can reduce tick vector numbers in a community. No vaccination exists.
National Reporting Requirements
- In the United States, the spotted fever group rickettsioses (including RMSF), ehrlichiosis, and anaplasmosis are all reportable on a national level.
- Potential tick-borne illness cases should be reported to state or municipal health offices.
- The health department should be able to assist with obtaining confirmatory laboratory tests. Staff from the health department may speak with the patient and healthcare provider to gather data for the surveillance case description.
- Although murine typhus is still reportable in at least 14 states, including DE, MA, NH, OH, and PA, typhus group rickettsioses are no longer considered to be nationally serious diseases.
- The laboratory notifies the specimen provider, CDC, and other appropriate authorities of the identification of R. prowazekii by phone, fax, or email, and must submit an APHIS/CDC Form 4 to CDC with the specimens, unless the HHS Secretary directs otherwise.
