DERMATOLOGIC MANIFESTATIONS OF ARTHROPOD-BORNE DISEASES

Mediterranean spotted fever associated with leucocytoclastic vasculitis and acute pancraeatitis

A young healthy gardener became febrile with abdominal pain, nausea, vomiting and diarrhoea followed by palpable purpura, mostly on the legs and buttocks with associated arthralgia. Dehydration, azotemia and hyponatraemia resolved with fluid replacement. Tests demonstrated acute pancreatitis, hepatitis, thrombocytopenia, microscopic haematuria and proteinuria. He improved with doxycycline, but bipedal pitting oedema and punctate rash involving the soles/hands appeared. Microbiological tests revealed positive IgM and IgG serology for rickettsiae spotted fever. Skin biopsy of the purpura confirmed leucocytoclastic vasculitis, positive for Rickettsiae conorii by PCR amplification. Palpable purpura is a rare important manifestation of Mediterranean spotted fever (MSF), due to either secondary leucocytoclastic vasculitis or associated Henoch-Schonlein purpura (HSP), which best explains the distribution of the rash, arthralgia, gastrointestinal symptoms, and microhaematuria not usually seen in R. conorii infections. Likewise, the patient's acute pancreatitis may be interpreted as a rare presentation of HSP or a seldom-encountered feature of MSF.

Syndromic classification of rickettsioses: an approach for clinical practice

Rickettsioses share common clinical manifestations, such as fever, malaise, exanthema, the presence or absence of an inoculation eschar, and lymphadenopathy. Some of these manifestations can be suggestive of certain species of Rickettsia infection. Nevertheless none of these manifestations are pathognomonic, and direct diagnostic methods to confirm the involved species are always required. A syndrome is a set of signs and symptoms that characterizes a disease with many etiologies or causes. This situation is applicable to rickettsioses, where different species can cause similar clinical presentations. We propose a syndromic classification for these diseases: exanthematic rickettsiosis syndrome with a low probability of inoculation eschar and rickettsiosis syndrome with a probability of inoculation eschar and their variants. In doing so, we take into account the clinical manifestations, the geographic origin, and the possible vector involved, in order to provide a guide for physicians of the most probable etiological agent.

Atypical Rocky Mountain spotted fever with polyarticular arthritis

BACKGROUND

Rocky Mountain spotted fever (RMSF) is an acute, serious tick borne illness caused by Rickettsia rickettsi. Frequently, RMSF is manifested by headache, a typical rash and fever but atypical disease is common, making diagnosis difficult. Inflammatory arthritis as a manifestation is rare. The purpose of this study is to describe a patient with serologically proven RMSF who presented in an atypical manner with inflammatory arthritis of the small joints of the hands and to review the previously reported patients with rickettsial infection and inflammatory arthritis.

METHODS

An 18-year-old woman presented with a rash that began on the distal extremities and spread centrally, along with hand pain and swelling. She had tenderness and swelling of the metacarpophlangeal joints on examination in addition to an erythematosus macular rash and occasional fever.

RESULTS

Acute and convalescent serology demonstrated R rickettsi infection. She was successfully treated with doxycycline.

CONCLUSIONS

Inflammatory arthritis is a rare manifestation of RMSF or other rickettsial infection with 8 previously reported patients, only 1 of whom had RMSF. Physician must have a high index of suspicion for RMSF because of atypical presentations.

Human arboviral encephalitis

Worldwide, arboviral illnesses constitute the most important international infectious threat to human neurological health and welfare. Before the availability of effective immunizations, approximately 50,000 cases of Japanese encephalitis occurred in the world each year, one-fifth of which cases proved lethal and a much larger number were left with severe neurological handicaps. With global climate change and perhaps other factors, the prevalences of some arboviral illnesses appear to be increasing. Arboviral illnesses, including Japanese encephalitis, tick-borne encephalitis, Yellow fever, and others, are emerging as possible global health care threats because of biological warfare. This chapter will review ecology, pathophysiology, diagnosis, management, and outcome of the forms of arboviral encephalitis that are of greatest importance in North America, together with some of the most important arboviral encephalitides prevalent in other parts of the world.

Murine typhus: an unrecognized suburban vectorborne disease

Murine typhus, an acute febrile illness caused by Rickettsia typhi, is distributed worldwide. Mainly transmitted by the fleas of rodents, it is associated with cities and ports where urban rats (Rattus rattus and Rattus norvegicus) are abundant. In the United States, cases are concentrated in suburban areas of Texas and California. Contrary to the classic rat-flea-rat cycle, the most important reservoirs of infection in these areas are opossums and cats. The cat flea, Ctenocephalides felis, has been identified as the principal vector. In Texas, murine typhus cases occur in spring and summer, whereas, in California, cases have been documented in summer and fall. Most patients present with fever, and many have rash and headache. Serologic testing with the indirect immunofluorescence assay is the preferred diagnostic method. Doxycycline is the antibiotic of choice and has been shown to shorten the course of illness.

Rocky Mountain spotted fever

Rocky Mountain spotted fever (RMSF) is a life-threatening disease caused by Rickettsia rickettsii, an obligately intracellular bacterium that is spread to human beings by ticks. More than a century after its first clinical description, this disease is still among the most virulent human infections identified, being potentially fatal even in previously healthy young people. The diagnosis of RMSF is based on the patient's history and a physical examination, and often presents a dilemma for clinicians because of the non-specific presentation of the disease in its early course. Early empirical treatment is essential to prevent severe complications or a fatal outcome, and treatment should be initiated even in unconfirmed cases. Because there is no vaccine available against RMSF, avoidance of tick-infested areas is still the best way to prevent the infection.

Rocky Mountain spotted fever

Rocky Mountain spotted fever (RMSF) is an unusual but important dermatological condition to identify without hesitation. The classic triad of headache, fever, and a rash that begins on the extremities and travels proximally to involve the trunk is found in a majority of patients. The cutaneous centripetal pattern is a result of cell to cell migration by the causative organism Rickettsia rickettsii. Such individuals should receive prompt antimicrobial therapy and supportive care to avoid serious and potentially fatal complications.

Rickettsial infections around the world, part 1: pathophysiology and the spotted fever group

BACKGROUND

The rickettsial diseases are an important group of infectious agents that have dermatological manifestations. These diseases are important to consider in endemic areas, but in certain suspicious cases, possible acts of bioterrorism should warrant prompt notification of the appropriate authorities.

OBJECTIVE

In this two part review article, we review these diverse diseases by examining established and up-to-date information about the pathophysiology, epidemiology, clinical manifestations, and treatment of the ricksettsiae.

METHODS

Using PubMed to search for relevant articles, we browsed over 500 articles to compose a clinically based review article.

RESULTS

Part one focuses on pathophysiology of the rickettsial diseases and the clinical aspects of the spotted fever group.

CONCLUSIONS

At the completion of part one of this learning activity, participants should be able to discuss all of the clinical manifestations and treatments of the sported fever group. Participants should also be familiar with the pathophysiology of the rickettsial diseases.

Treatment and prevention of rickettsial and ehrlichial infections

Rickettsial and ehrlichial infections are both carried by arthropod vectors. Both Rickettsia and Ehrlichia are small intracellular gram-negative coccobacilli. Clinical manifestations of Rickettsia range from spotted fevers to various forms of typhus. Human ehrlichiosis can present as monocytic ehrlichiosis or granulocytic anaplasmosis. Prevention is by avoidance of the responsible vectors. Therapy is usually with doxycycline, but chloramphenicol can also be used.

Dermatoses from ticks

Ticks are ectoparasites that cause dermatologic disease directly by their bite and indirectly as vectors of bacterial, rickettsial, protozoal, and viral diseases. In North America, where ticks are the leading cause of vector-borne infection, dermatologists should recognize several tick species. Basic tick biology and identification will be reviewed. Tick bites cause a variety of acute and chronic skin lesions. The tick-borne diseases include Lyme disease, tick-borne relapsing fever, tularemia, babesiosis, Rocky Mountain spotted fever, other spotted fevers, ehrlichiosis, Colorado tick fever, and others. The epidemiology, clinical features, diagnosis, and treatment of these diseases are reviewed with an emphasis on cutaneous manifestations. Finally, the prevention of diseases caused by ticks is reviewed.

Tularemia and Q fever

The zoonotic infections caused by Francisella tularensis and Coxiella burnetii, tularemia and Q fever, respectively, are two less commonly encountered clinical illnesses that are becoming increasingly recognized as epidemiologically important human diseases. The prevalence of tularemia and Q fever can be positively impacted by increased awareness of the clinical entities that arise from infection by these arthropod-borne organisms. Improved recognition of these clinical syndromes will lead to greater diagnostic accuracy in recognizing these diseases in patients. Ultimately, more stringent measures to prevent infection may be required, through raising public awareness, since current therapeutic regimens for these two diseases are limited, and knowledge of the pathogenesis of these two organisms are still in developing stages.

Rickettsia associated with male-killing in a buprestid beetle

Many populations of the buprestid leaf-mining beetle, Brachys tessellatus, from central South Carolina, USA, show highly skewed sex ratios, ranging from 1.3 to 6.0 females per male. We have identified a Rickettsia bacterium that is associated with sex ratio distortion (SRD) and selective killing of male embryos in B. tessellatus. Molecular assays of infection by this bacterium are highly associated with SRD within families, and treatment with an antibiotic (tetracycline) increases the number of male eggs that hatch and develop. The 16S rDNA sequence indicates that this is a novel Rickettsia, most closely related to Rickettsia bellii (a tick-associated bacterium) and a pea-aphid Rickettsia. It is also related to a Rickettsial bacterium that causes male-killing in an unrelated ladybird beetle species. Low levels of parthenogenesis are also observed in this system (about 10% of females) and may be the result of selection due to male rarity, or a direct result of infection by the Rickettsia.

Tick-borne pulmonary disease: update on diagnosis and management

Ticks are capable of transmitting viruses, bacteria, protozoa, and rickettsiae to man. Several of these tick-borne pathogens can lead to pulmonary disease. Characteristic clinical features, such as erythema migrans in Lyme disease, or spotted rash in a spotted fever group disease, may serve as important diagnostic clues. Successful management of tick-borne diseases depends on a high index of suspicion and recognition of their clinical features. Patients at risk for tick bites may be coinfected with two or more tick-borne pathogens. A Lyme vaccine has recently become available for use in the United States. Disease prevention depends on the avoidance of tick bites. When patients present with respiratory symptoms and a history of a recent tick bite or a characteristic skin rash, a differential diagnosis of a tick-borne pulmonary disease should be considered. Early diagnosis and appropriate antibiotic therapy for these disorders lead to greatly improved outcomes.

Serious waterborne and wilderness infections

Serious waterborne and wilderness infections are common and usually treatable if diagnosed early. The differential diagnosis for these infections requires a careful and thorough history and physical examination. Common clinical presentations include acute febrile illnesses, altered mental status, diarrhea, or pneumonia. Pathogens causing serious infections include bacteria, fungi, viruses, and protozoa. Epidemiologic help can be obtained from local or state health departments as well as the Centers for Disease Control.

Skin problems in the traveler

Skin lesions are common in travelers and include a mix of mundane dermatologic problems and rare diseases acquired only in remote or tropical regions. The morphology, distribution, and progression of the lesions are useful in assessing possible causes. Early in the evaluation it is important to determine whether the patient might have a process that is rapidly progressive, treatable, or transmissible. In addition to routine laboratory studies, biopsy and serologic tests are often necessary to confirm a specific diagnosis.

Rickettsialpox

Rickettsialpox is a member of the spotted-fever group of the rickettsioses and results from an infection with Rickettsia akari. This microbe is transmitted by the bite of the house-mouse mite Liponyssoides sanguineus. Patents experience fevers, sweats, headaches, and a vesicular eruption over the trunk and extremities. The palms and soles are spared. An eschar results at the spot of the mite bite. Tetracycline is the treatment of choice.

Willy Burgdorfer: Lyme disease

The documented history of erythema migrans dates to 1909, when Arvid Afzelius described a case of this skin lesion at a dermatologic meeting in Sweden. He felt that the eruption was likely produced by the bite of a tick. The initial description of Lyme arthritis appeared in 1977, and a number of the patients described in this series developed a rash thought to be erythema migrans. Four years later, Burgdorfer discovered the presence of spirochetes (subsequently named Borrelia burgdorferi) in ticks from an endemic locus of Lyme arthritis and determined this to be the causative organism of the disease. Lyme disease is the most common tickborne infection in the United States. Its natural course has been divided into three clinical stages. The infection begins with a rash and flulike symptoms and may progress after days to weeks to a disseminated stage and in months to years to a late stage. There is little information (except erythema migrans) about the clinical features of the illness that is specific for Lyme disease. There are a number of effective antibiotic treatment regimens, and although acute infection generally responds well to treatment, management of chronic illness with antibiotics has been less consistently successful. With respect to antibiotic prophylaxis, the few studies performed have led to the conclusion that, even in endemic areas, the risk of infection is so low that routinely instituting treatment following a tick bite is not warranted.