Lice and Scabies: Treatment Update — American Family Physician

Lice and Scabies: Treatment Update

KAREN GUNNING, PharmD, University of Utah College of Pharmacy, Salt Lake City, Utah

BERNADETTE KIRALY, MD, and KARLY PIPPITT, MD, University of Utah School of Medicine, Salt Lake City, Utah

Am Fam Physician. 2019 May 15;99(10):635-642.

Patient information: See related handout on lice and scabies, written by the authors of this article.

Author disclosure: No relevant financial affiliations.

Article Sections

Pediculosis and scabies are caused by ectoparasites. Pruritus is the most common presenting symptom. Head and pubic lice infestations are diagnosed with visualization of live lice. Nits (lice eggs or egg casings) alone are not sufficient to diagnose a current infestation. A “no-nit” policy for return to school is not recommended because nits can remain even after successful treatment. First-line pharmacologic treatment for pediculosis is permethrin 1% lotion or shampoo. Newer treatments are available but costly, and resistance patterns are generally unknown. Noninsecticidal agents, including dimethicone and isopropyl myristate, show promise in the treatment of pediculosis. Extensive environmental decontamination is not necessary after pediculosis is diagnosed. In adults, the presence of pubic lice should prompt an evaluation for sexually transmitted infections. Body lice infestation should be suspected in patients with pruritus who live in crowded conditions or have poor hygiene. Scabies in adults presents as a pruritic, papular rash in a typical distribution pattern. In infants, the rash can also be vesicular, pustular, or nodular. First-line treatment for scabies is permethrin 5% cream. Clothing and bedding of persons with scabies should be washed in hot water and dried in a hot dryer. Counseling regarding appropriate diagnosis and correct use of effective therapies is key to reducing the burden of lice and scabies.

Pediculosis and scabies are caused by ectoparasites. Pruritus is the most common presenting symptom with both conditions. Determining the specific etiology of pruritus based on history and physical examination findings is important. Lice in particular may be overdiagnosed by anxious patients and treated using over-the-counter medications without an office evaluation.1 Seeking an appropriate clinical diagnosis may help reduce treatment-resistant lice. Although the diagnosis of pediculosis and scabies has not changed substantially, there are new developments in treatment since this topic was previously covered in American Family Physician .2 – 4

SORT: KEY RECOMMENDATIONS FOR PRACTICE

A “no-nit” policy is not recommended for schools and day cares because nits alone do not indicate an active infestation. Children should not be kept out of school during treatment, even with active infestation, because the likelihood of transmission is low, and this can result in significant absences.

U.S. and Canadian consensus guidelines based on basic knowledge of the lice life cycle

Permethrin 1% lotion or shampoo (Nix) is first-line treatment for pediculosis. Alternative treatments should not be used unless permethrin fails after two treatments.

U.S. consensus guidelines balancing effectiveness and toxicity

Nonovicidal therapies for pediculosis should be applied twice, seven to 10 days apart, to fully eradicate lice. Some authors postulate that three treatments with permethrin or pyrethrins might be most effective.

U.S. and Canadian consensus guidelines based on basic knowledge of the lice life cycle Inappropriate retreatment may result in resistance and lack of treatment effectiveness

Scabies should be considered in patients with a pruritic, papular rash in the typical distribution and pruritus in close contacts. The classic burrows in webs and creases may not be present.

U.S. and European consensus guidelines based on epidemiologic data and case studies

Oral ivermectin (Stromectol) should be reserved for patients with scabies who do not improve with permethrin 5% cream (Elimite).

Guidelines using consensus agreement in area of little clinical research

A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.

SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendation Evidence rating References Comment

A “no-nit” policy is not recommended for schools and day cares because nits alone do not indicate an active infestation. Children should not be kept out of school during treatment, even with active infestation, because the likelihood of transmission is low, and this can result in significant absences.

U.S. and Canadian consensus guidelines based on basic knowledge of the lice life cycle

Permethrin 1% lotion or shampoo (Nix) is first-line treatment for pediculosis. Alternative treatments should not be used unless permethrin fails after two treatments.

U.S. consensus guidelines balancing effectiveness and toxicity

Nonovicidal therapies for pediculosis should be applied twice, seven to 10 days apart, to fully eradicate lice. Some authors postulate that three treatments

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Pediculus humanus

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Infectious Diseases of the Skin

Anca G. Prundeanu Croitoru, . Klaus J. Busam, in Dermatopathology , 2010

Clinical Findings

Pediculus humanus capitis (the head louse) usually infests children age 3 to 12 years. Transmission occurs through close contact or contact with fomites. Nits ( Fig. 3-99 ) are found more often in the occipital and retroauricular areas, and combing makes identification easier. Body louse (Pediculus humanus humanus) affects mainly the homeless in urban areas. It acts as a vector for Bartonella quintana, producing fever and endocarditis. Worldwide, body lice are important, especially among the poor and refugees, and may act as vectors for relapsing fever, trench fever, and epidemic typhus. Crab louse (Pthirus pubis) infestation is commonly sexually transmitted. Up to one third of patients may have another concomitant sexually transmitted disease. The crab louse attaches to hair on pubis, trunk, legs, and buttocks, and infrequently to scalp hair. Secondary to bites, characteristic blue-gray macules (maculae caeruleae) appear on the lower abdomen and thighs.

FIGURE 3-99 . Pediculosis. A, Note the white nit on the hair shaft. B, Nit at close-up view.

Bartonellosis, Cat-scratch Disease, Trench Fever, Human Ehrlichiosis

Transmission of Bartonella quintana

Pediculus humanus humanus has been the identified vector of B. quintana for several decades. Lice infected with B. quintana appear to remain so until they die, although their lifespan apparently does not decrease. P. humanus corporis lives in clothes and is associated with poverty and lack of hygiene. In a research of 930 homeless persons, that took place in Marseille, lice infestation was present in 22% and was associated with hypereosinophilia. 32 Pediculosis (lice infestation) is transmitted by contact with clothes or bedding. B. quintana multiplies in the louse’s intestine and is transmitted to humans by faeces through altered skin. 33 Body lice usually feed 5 times a day and inject biological proteins with their bites, including an anaesthetic that provokes an allergic reaction and leads to pruritus and scratching, which facilitates the faecal transmission of B. quintana, and persistent B. quintana bacteraemia facilitates its spread by lice. 34 Historically, infection with B. quintana was thought to be limited to people with human body louse exposure. However, recently B. quintana was identified in head lice from homeless children in Nepal; 35 in head lice from homeless adults in San Francisco; 36 and in head lice nits from homeless people. 37 Ctenocephalides felis appears to be a potential vector for B. quintana 38 and it is possible that the cat fleas can maintain infection with B. quintana and transmit the organism among cats, which can subsequently transmit B. quintana to people via a bite or scratch. 39 Recently, the understanding of the epidemiology of B. quintana as an emerging source of human infection has changed as B. quintana was isolated from a non-human research primate (Macaca fascicularis Raffles) and from dogs with endocarditis. 22 Moreover, the bacterium was detected in cat fleas 38 and in cat dental pulp, 40 which suggests bacteraemia in cats, and has been isolated in a patient who owned a cat and sought treatment for chronic adenopathy. 41 B. quintana was also detected in Pulex irritans (Linnaeus) removed from a pet Cercopithecus cephus (Linnaeus) monkey in Africa. 42

Pathogenesis

Trench fever is characterized by intracellular erythrocyte parasitism of B. quintana ( Figure 30.2 ), the proportion of which varies between 0.001% and 0.005%. 43 Bacteria can also be seen either extracellularly, in mature erythrocytes or in erythroblasts. 44 This intracellular erythrocyte parasitism can probably preserve the pathogens for efficient transmission by body lice, protect B. quintana from the host immune response, and contribute to decreased antimicrobial efficacy. This immune evasion might explain the frequent relapses seen after antibiotic treatment of such patients.

Figure 30.2 . Intracellular erythrocyte parasitism of B. Quintana.

Bartonella endocarditis causes significant destruction of the valvular cusps which is characterized by mononuclear cell inflammation, extensive fibrosis, large calcification and small vegetation. 45 Lepidi and colleagues identified that more than half of the patients with Bartonella endocarditis had pre-existing valvular disease that could lead to the development of degenerative changes, especially fibrosis, calcification and chronic inflammation, independent of the infective process. 45 The bacteria are seen extracellularly in dense immunopositive clusters mainly included in vegetations and intracellularly in neutrophil and macrophage cytoplasms. 46 Patients with Bartonella endocarditis have a higher death rate and undergo valvular surgery more frequently than patients with endocarditis caused by other pathogens. 47

Trench Fever

Clinical manifestations may range from asymptomatic infection to severe, life-threatening illness. After an incubation period of 2–3 weeks, there is a sudden onset of fever that lasts 1–3 days and is associated with headache, shin pain and dizziness. 48 Often there is tachycardia, marked conjunctival injection in 95% of subjects, myalgia, arthralgia and severe pain in the neck, back and legs, especially the tibia (shinbone fever). Several crops of erythematous macules or papules measuring 1 cm or less on the abdomen, chest and back may occur in 70–80% of patients. Symptoms are most severe during the initial episode, diminishing with each subsequent attack except bone pain, especially in the shins, which usually grows more severe with each attack. Although fatal cases have not been reported, the disease may persist for 4–6 weeks and result in prolonged disability. Relapses may occur years later and in some cases, there may be bacteraemia with no clinical signs. Persistent bacteraemia has long been also associated with B. quintana infection and Kostrzewski showed that B. quintana was present in the blood of trench fever patients up to 8 years after initial infection. 49

Endocarditis

Bartonella bacteraemia may result in endocarditis mostly in people with existing heart valve abnormalities. The most common identified agents of Bartonella endocarditis are B. quintana, followed by B. henselae. 50 B. quintana endocarditis mostly develops in persons without any previous valvular injuries; known risk factors are alcoholism, homelessness and body lice infestation. B. henselae endocarditis patients frequently have a previous valvulopathy, and disease is associated with cat bites or scratches and cat flea exposure. However, sporadic cases of endocarditis have been also associated by B. koehlerae, B. vinsonii subsp. berkoffii, B. vinsonii subsp. arupensis, B. elizabethae and B. alsatica. 51 Patients with endocarditis tend to have pre-existing heart valve disease that promotes the development of infective endocarditis, and in some cases, a definite risk factor for infection specifically with Bartonella is present. Patients appear to have chronic, blood culture-negative endocarditis; fever is usually present (90%), a vegetation is usually observed on echocardiography (90%) and >90% of patients require valvular surgery. 47

Cat-scratch Disease

B. henselae was discovered a quarter of a century ago as the causative agent of cat-scratch disease (CSD), a clinical entity described in the literature for more than half a century.

Lice (Pediculosis)

Therapy

Both Pediculus humanus species (head and body lice) and Phthirus pubis (the crab or pubic louse) have now demonstrated high levels of resistance worldwide to the safest topical pediculicides, specifically the natural pyrethrins and synthetic pyrethroids (permethrin, phenothrin). 5,7-11 In addition, resistance to lindane, an organochlorine insecticide, and malathion, an organophosphate insecticide, both alone and combined with pyrethroids, has been reported in the United Kingdom and elsewhere. 5,7 In a randomized comparison of wet combing versus 0.5% malathion shampoos for head lice in the United Kingdom, Roberts and colleagues reported a 78% cure rate for malathion shampoo versus 38% for wet combing. 7 In an in vitro pediculicidal efficacy comparison of five pediculicides available in the United States, Meinking and associates reported the following results: (1) there were significant differences in the pediculicidal efficacies of the five pesticides tested; (2) malathion was the only tested pesticide in their study that had not become less effective as a pediculicide; (3) the ranked order of therapeutic effectiveness from most to least effective was 0.5% malathion, undiluted natural pyrethrins with piperonyl butoxide, 1% permethrin, diluted natural pyrethrins with piperonyl butoxide, and 1% lindane; and (4) some head lice in the United States had become resistant to most pediculicides. 8

The increasing resistance of head lice to the pyrethrins and pyrethroids has led to the increasing use of more toxic pesticides, specifically lindane, malathion, and carbaryl (not approved by the U.S. Food and Drug Administration [FDA] in the United States) in treating pyrethroid-resistant pediculosis capitis worldwide. 7,10,11 Lindane is being inappropriately overprescribed, especially for recurrent infestations with lindane-resistant head lice. 5,12 Lindane is an organochlorine insecticide that bioaccumulates in adipose and nerve tissue with overapplication or, if ingested, can cause seizures, especially in children. 5,8 Although malathion, an organophosphate pesticide, has demonstrated the greatest therapeutic efficacy against head lice in the United States, it is an irreversible acetylcholinesterase inhibitor that can cause a cholinergic toxidrome and fatal neuromuscular paralysis after overapplication or ingestion. 10 Carbaryl, a carbamate pesticide, highly effective against both head lice and scabies, is being increasingly prescribed for pediculosis capitis outside the United States, especially in the United Kingdom and Europe. 11 Carbaryl is a reversible (nonaging) acetylcholinesterase inhibitor that is closely related to the organophosphate pesticides that can also cause a cholinergic (muscarinic and nicotinic) toxidrome after overapplication or ingestion.

Unfortunately, all the topical pesticides used to treat ectoparasitic infections share the same three characteristics as the three most commonly ingested childhood poisons: (1) prescribed, often over-the counter (OTC), medications, (2) household products, and (3) pesticides. 11 As the prevalence of ectoparasitic infections with pesticide-resistant ectoparasites increases, alternative pesticides, more toxic than pyrethrins and pyrethroids, will be prescribed for ectoparasitic infestations, medications will continue to be administered in households, and household accidental overapplication or ingestion of more toxic pesticide formulations for pediculosis may increase without enhanced public health education measures. 11,13

A descriptive meta-analysis of pesticide poisonings in children in the United States over the period 1966 to 2008 demonstrated that malathion pediculicide ingestions were increasing, possibly as a result of increasing pyrethroid-resistant head lice infestations. 11 Subsequently, a state health department analysis of pesticide exposures in children younger than 7 years of age over the period 2003 to 2007 reported that lice shampoo exposures by ingestions, intraocular instillations, and prolonged topical applications were second only to mosquito-repellent exposures and resulted in more medical visits than all other pesticide exposures. 13

Therapy for Pediculosis Capitis

Management of pediculosis capitis includes two topical or systemic treatments with pediculicides, 7 to 10 days apart, and removal of all viable nits by carefully combing wet hair. Olive oil, petroleum jelly, and HairClean 1-2-3 are preferred hair-wetting agents, and plastic combs are preferred over metal combs. Unfortunately, the ideal pediculicide with 100% killing activity against lice and nits does not exist. Table 294-1 presents the most commonly used pediculicides for lice infestations. As noted, drug resistance is increasing against the safest pediculicides, the pyrethrins and synthetic pyrethroids, and even against lindane and malathion, an effective ovicidal insecticide with 95% efficacy against viable nits. 5,7,8

A randomized controlled trial has now demonstrated that a single oral dose of ivermectin, 400 µg/kg of body weight repeated at 7 days, established higher louse-free rates by day 15 than 2 applications of 0.5% malathion lotion in patients with pyrethroid-resistant head lice infestations. 14 In 2012, the FDA approved the use of topical 0.5% ivermectin lotion for head lice infestations after two multisite, randomized, double-blind studies comparing single applications of 0.5% ivermectin lotion with vehicle control that demonstrated significantly greater louse-free days at 1, 7, and 14 days in the ivermectin group than in the vehicle control group. 15 Today, both oral ivermectin (although not FDA approved) and topical ivermectin lotion for head lice offer convenient, single-dose treatments that kill nymphs when they emerge from nits and can be reserved for drug-resistant head lice cases to limit the potential for ivermectin resistance.

Therapy for Body Lice

Management includes initial bathing with soap and water, followed by two topical or systemic treatments with pediculicides, 7 to 10 days apart (see Table 294-1 ). Topical medications should be applied to clean affected areas, allowed to dry, and not rinsed for 8 (malathion) to 24 (pyrethrins, pyrethroids) hours.

Arthropods of Public Health Importance

Human Body Lice

Body lice ( Pediculus humanus humanus, sometimes called Pediculus humanus corporis) usually infest people who live in unhygienic, crowded conditions and are unable to bathe or change clothes regularly. Their eggs (nits) are found in the seams of human clothing. They transmit bacterial diseases such as trench fever, typhus and louse-borne relapsing fever in places where war, poverty, and unsanitary conditions exist. Their bites cause intense irritation, itching, and allergies. People with chronic body lice infestations develop a skin thickening and discoloration called vagabond or hobo disease. Good hygiene and regularly washing clothing and bedding will prevent infestations, and chemical pediculicides can treat body lice infestations.

Acquired Rashes in the Older Child

Kristen E. Holland, Paula J. Soung, in Nelson Pediatric Symptom-Based Diagnosis , 2018

Pediculosis

Lice are ectoparasitic insects. Pediculus humanus capitis, the head louse, causes the most common form of louse infestation. This occurs more often in whites; girls are more susceptible than boys. Because the head louse can survive for more than 2 days off the host’s scalp, the condition can be transmitted via shared hats, combs, brushes, towels, or bedding. On physical examination, the nits (ova) can be found close to the scalp on the proximal hair shafts. They appear as small, oval, whitish bodies approximately 0.5 mm in length. They adhere tightly to the hair shaft and are not easily removed. The nits can be more readily identified by their fluorescence under a Wood lamp. Microscopic examination of the proximal hair shaft may further aid in recognition of the nits. The infestation is characterized by intense pruritus, especially at night.

Some sources start treatment of pediculosis capitis with over-the-counter topical application of 1% permethrin shampoo or pyrethrin combined with piperonyl butoxide products, both of which have good safety profiles. However, resistance to these products has been documented. In treatment failures or known resistance, additional topical agents such as malathion 0.5%, benzyl alcohol, spinosad, and ivermectin lotions are options. Oral ivermectin may be used when lice are resistant to all topical agents. However, each agent’s recommended age, weight, and safety profile need to be considered.

It is extremely important to wash and dry (on a hot cycle) all exposed bedding and clothing. All combs and brushes should be soaked in the pediculicide for 15 minutes, and all items that cannot be machine-washed with hot water or dry-cleaned should be placed in plastic bags for 2 weeks. All household members should be treated at the same time. Nits must be removed with a fine-toothed comb after application of a damp towel to the scalp.

Parasitology

Lice and mites

Humans are hosts to the head louse ( Pediculus humanus capitis), the body louse (Pediculus humanus humanus), and the crab louse (Phthirus pubis). Lice attach to hair shafts and lay eggs (nits). Lice derive nutrients through tissue by blood-feeding and cause itching and irritation ( Fig.16-7 ). They are readily treatable with over-the-counter chemical applications.

Figure 16-7 . A, The common head and body louse (Pediculus humanus). B, The crab louse (Phthirus pubis).

Mites are related to ticks and spiders. There are many species, with commonalities in biting and bloodsucking behavior causing irritation and discomfort; many species are also known to elicit allergic reactions. Mites are spread by direct contact. Common mites that affect human hosts include Sarcoptes scabiei (scabies), Eutrombicula alfreddugesi (chiggers), and Dermatophagoides pteronyssinus and Dermatophagoides farinae (house dust mites). Treatment can be as simple as administration of oral antihistamines and application of hydrocortisone cream to relieve associated symptoms.

Liver

The liver is a filter for toxic metabolites. The parenchyma is comprised of liver plates (hepatocytes) with endothelial cells establishing sinusoids for blood flow. The characteristic portal triad contains at least one profile each of a hepatic artery, a portal vein, and an interlobular bile duct.

Skin disorders

Pediculosis

Three species of Pediculosis (lice) infest humans: Pediculus humanus capitis (head lice), Pediculus humanus corporis (body lice) and Phthirus pubis (pubic lice, also known as crab lice). Transmission is by close person-to-person contact or by sharing clothing, hats or combs. Elderly individuals who have poor personal hygiene or who live in an overcrowded environment are at risk for head and body lice. Pediculosis capitis presents with scalp pruritus, which can progress to eczematous changes with impetiginization. Localized lymphadenopathy may occur. Examination reveals small, gray-white nits (ova) adherent to hair shafts. Adult lice can occasionally be found. Pediculosis corporis should be considered in a patient who presents with generalized pruritus. Secondary eczematous changes, excoriation and impetiginization can occur. Lice and nits are usually not found on the body but rather in the seams of clothing. Phthirus pubis is usually spread by sexual contact, but may also be transmitted via clothing or towels. The bases of pubic hairs should be examined for lice and nits in a patient complaining of pubic pruritus.

Head lice are treated with 1% lindane shampoo, which is applied for 4 minutes and then washed off. Treatment should be repeated once in 7–10 days. Close contacts should also be examined and treated. Combs and brushes should be soaked in lindane shampoo for 1 hour. The presence of nits after appropriate treatment does not signify treatment failure. They can be removed from the hair with a fine-tooth comb dipped in vinegar.

Body lice are treated by washing the affected clothing in hot water, dry-cleaning them or placing them in a hot dryer and then ironing the seams. Alternatively, the clothing can be disinfected with an insecticidal powder such as DDT 10% or malathion 1%. If lice or nits are found on the skin, the patient can wash with lindane shampoo as above. Pubic lice are treated identically to head lice, with local application of lindane shampoo. In all forms of infestation, pruritus and dermatitis can be treated with emollients and topical steroids, and impetiginization may require antibiotics.

Relapsing Fever and Other Borrelia Diseases

Ecology and Epidemiology of Louse-Borne Relapsing Fever

The vector is the body louse ( Fig. 44.3 ), Pediculus humanus corporis, which only feeds on humans in nature. B. recurrentis appears to be a louse-adapted variant of the tick-borne species B. duttonii. 26 Nonhuman primates can be experimentally infected with B. recurrentis, but humans are the critical reservoirs for maintenance of the pathogen in nature. After entering the midgut of the feeding louse, B. recurrentis move to the hemolymph where they may persist for the approximately 3-week life span of the louse. They do not migrate to the salivary glands or appear in the feces. Humans become infected with B. recurrentis when they crush an infected louse with fingers or teeth. The organism is introduced at the bite site, the skin of the crushing fingers, the conjunctivae when people rub their eyes, or through the mucous membranes of the mouth.

Figure 44.3 . Life cycle of louse-borne relapsing fever.

B. recurrentis infection still occurs in the Horn of Africa, particularly in the highlands of Ethiopia, where it has been endemic for decades. 3,27–29 Transmission is highest during the rainy season when the poor gather together in shelter, and infected lice move from one person to another. As reflected by such colloquial names as “famine fever” and “vagabond fever,” factors that predispose to louse-borne relapsing fever epidemics include famine, war, and refugees. Precipitating conditions for outbreaks are crowding, limited changes of clothing, and lack of access to washing. Millions of cases of louse-borne relapsing fever occurred around the disrupted times of the two world wars of the twentieth century.

Epidemic Louse-Borne Typhus

Natural History, Pathogenesis, and Pathology

In 1909 Charles Nicolle observed the role of the body louse Pediculus humanus subsp. corporis (or P. humanus subsp. humanus) in the transmission of epidemic typhus. Lice become infected when feeding on the blood of a bacteremic patient. Transmission between human hosts is associated with close human contacts; primary infection occurs when R. prowazekii is transmitted from the vector to the host, not by louse bites, but by contamination of bite sites, scratching lesions, conjunctivae, and mucous membranes (including the respiratory tract) with the infectious feces or crushed bodies of infected lice. These infested aerosols constitute a source of infection of typhus for clinicians in contact with lice-infested patients. In the case of Brill–Zinsser disease, recrudescent infection of the human host is associated with bacteremia; if louse infestation of the patient occurs at the same time, lice become infected through host feeding, and if appropriate conditions exist, an outbreak can occur. 3

It was previously thought that humans were the only reservoir of R. prowazekii and human body lice the only vectors. But since the 1950s, specific antibodies have been detected in, and the bacterium isolated from, several domestic and wild animals. Ticks might be a reservoir for R. prowazekii, as Amblyomma spp. and Hyalomma spp. were found to be infected in Mexico and Ethiopia, respectively. 3 Of particular interest is the reservoir formed by flying squirrels (Glaucomys volans). Reported cases of epidemic typhus in the United States have been associated with contact with flying squirrels. 4 The role of animal reservoirs in the global burden of typhus is currently not well defined. After entering the body of an infected human, the bacteria spread through blood and lymph, then they infect endothelial cells of the small capillaries. Rickettsial infection leads to endothelial damage, which is associated with widespread vasculitis; the clinical signs and symptoms relate to the affected organs. Endothelial injury can also lead to micro- and macroscopic foci of hemorrhages. Vasculitis can also be associated with thrombi in small vessels and surrounding inflammatory infiltrates. These correspond to typhus nodules and may occur focally throughout the central nervous system (CNS); these lesions explain the neurologic features commonly associated with epidemic typhus. 3 The vasculitis of R. prowazekii infection is generalized, and thus any organ may be involved.

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Clinical recommendation Evidence rating References Comment