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Infectious Diseases

BED BUGS 39250129​

  • Cimex lectularius​, Cimex hemipterus

  • 5mm ovoid wingless insects

  • nocturnal, live in dark environments: mattresses, furniture, flooring, walls, etc.

  • bedbug sniffing dogs can confirm presence; traps can also be placed to trap bedbugs for confirmation

  • do not appear to be a vector of communicable diseases

  • eradication by pest management professionals is recommended but can be costly (~$1225 for a single family home)

DERMATOPHYTE INFECTIONS

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Dermatophytosis Resistance                                                                                                                                                                       

  • Resistant dermatophyte infection resistance is becoming more common according to the CDC, attributed to the inappropriate use of topical antifungals and antifungal/steroid combinations.    

  • A common strain being reported is trichophyton indotineae.  It requires genomic sequencing for identification, and is frequently misidentified as trichophyton metagrophytes or inderdigitale.

  • Although likely an overestimate given the sample was taken from a reference laboratory, one study demonstrated 18.6% terbinafine resistance (MIC >0.5 micro g / mL), equally split between T. rubrum and T. indotineae. Itraconazole resistance was rare. (37432126)

  • Fungal infections resistant to traditional antifungals can be reported to the CDC: FungalOutbreaks@cdc.gov.

Trichophyton Indotineae (aka, mentagrophytes internal transcribed spacer genotype VIII)

  • Trichophyton metagrophytes internal transcribed spacer genotype VIII, aka Trichophyton indotineae, is a newly identified dermatophyte that has lead to chronic, severe, refractory dermatophyte infections primarily in South Asia, though it has been reported globally.  It can often be resistant to terbinafine and slow to respond to griseofulvin and azoles.  Preferred treatment is itraconazole for 6-8wks or longer.  Post-tinea xerosis and itch persistence may occur.  (37418257) 

  • Documented to likely spread by close physical contact, including sexual.

Treatment

  • First line is oral itraconazole 200mg daily for 6-8 weeks or longer.  Fluconazole, voriconazole, and posaconazole may also be tried.  Higher doses of terbinafine (500mg daily) may also be effective.  Itraconazole 400mg daily for 1 week per month for several consecutive months is another treatment approach. (Dermatology World, June 2024)

  • Topical options include ciclopirox, tavaborole, and efinaconazole. 

MOLLUSCUM CONTAGIOSUM

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Treatment                                                                                                                                                                                                       

Cantharadin​

  • VP-102 is a new drug-device combination that consists of an ampule of gentian violet/cantharadin/bittering agent mixture for application to molluscum.  It was applied every 21 days until lesion clearance or up to 4 treatments.  Assessed after 12 weeks, treatment was much more effective than vehicle, with ~50% clearance in treatment groups compared to ~15% in vehicle groups (2 parallel studies were published).  Side effects were common, with discoloration occurring in 1/4-1/3 of patients.  (32965495)

MONKEYPOX 36757705

Cause and Transmission

  • The accepted term will be Mpox after late 2023 (very strange in my opinion). 

  • Orthopoxvirus closely related to smallpox.

  • 3 genomic variants: clade I, IIa, and IIb.  Before 2019, most cases were clade I in Central Africa.  Clade IIb, however, is the cause of the 2022 multinational outbreak.  

  • Most cases are in MSM in which coinfection with HIV is 26-52%, but overall prevalence rates or proportion of cases in MSM vs other were not published the article referenced here (36757705). 

  • Lesions are highly infectious until complete reepithelialization (in contrast to HSV, in which crusted lesions have low infectivity).

  • Lesions are primarily via skin to skin contact, but also respiratory secretions during prolonged close contact. 

Disease Characteristics of Clade IIb Mpox​

  • Lesions evolve from small red macules to large umbillicated papules with concentration around the mouth, hands, and anogenital area; clade IIb manifestations often less striking in morphology than clade I, and lesions numbering 10 or fewer.

  • Prodromal symptoms and lymphadenopathy is much less common than it is in clade I disease, for which they are common.

  • Mortality is very uncommon in clade IIb (<0.05%) vs clade I (10%) do to possible differences in virulence of the virus but also host and other socilogical determinants.  

Diagnosis and Management​

  • In addition to clinical factors, swabbing the surface of the lesion for PCR testing.  Unroofing lesions is not recommend as it is not necessary.

  • Gentle cleansing, maintain lesions moist with vaseline. 

  • No FDA approved treatments, but tecovirimat for smallpox has been used as well as cidofovir and brincidofovir.  No clear treatment guidelines are available. 

  • 2 smallpox vaccines are currently available for the prevention of mpox, and may be offered for high risk individuals or after exposures.

SCABIES 39250129​

 

Background                                                                                                                                                                                                   

  • Caused by: Sarcoptes scabiei var hominis

  • Lifecycle: 14-days: females lay eggs, eggs hatch after 3-4 days and develop into adults in 7-14 days at which time the females again lay eggs

  • 1-15 minutes typically present in common scabies; thousands to millions in crusted (Norwegian) scabies

  • Transmission requires 15-20 minutes of direct skin to skin contact; transmission via fomites is rare except for crusted (Norwegian) scabies

Clinical presentation                                                                                                                                                                                     ​

  • Hypersensitivity reaction occurs in 4-6 weeks ands is responsible for the majority of signs and symptoms; can occur within 24 hours after repeat exposure.                                                                                                                                                                                                                            

  • Manifestations may be varied and non-specific findings consist are largely eczematous: papules and nodules, lichenified plaques, excoriations, etc.  Burrows are nearly pathognomonic.  

  • One study (39250129 ref 20) reported over half of those affected by scabies may be asymptomatic.

  • Pruritus may be minimized in those who are immunosuppressed, who are also more likely to develop crusted scabies. 

Diagnosis                                                                                                                                                                                                       

  • 3 levels of diagnostic certainty: confirmed, clinical, suspected.

    • Confirmed = visualization of mites, eggs, or feces, either by light microscopy (wet prep, biopsy), or other magnification (dermoscopy).  

    • Clinical = presence of burrows, genital lesions in men (highly specific), or typical distribution + itch + positive contact history.

    • Suspected = typical lesions/distribution with itch OR positive contact history, or, atypical lesions/distribution with itch AND positive contact history

  • Wet prep: perform with mineral oil (better refractive properties because of viscosity, and KOH will dissolve feces and decrease mite mobility.  Burrows are highest yield lesions to recover mites, vesicular lesions nodules are also high yield.

  • Eosinophilia is a supportive finding. 

Treatment                                                                                                                                                                                                       

​Topical

  • Permethrin 5% cream; crotamiton 10% lotion, spinosad 0.9% suspension, benzyl benzoate, lindane, sulfur

  • Permethrin is by far the most effective, with a >80% cure rate 3-6 weeks after treatment. However, it can cause significant irritation and itching.

    • Dosing: apply from neck to toes (scalp to toes in infants) and leave on for 8-14 hours.  Rinse.  Repeat in 1-2 weeks.​

Oral/Systemic​​​

  • Ivermectin is not FDA approved for scabies. 

    • Dosing: 0.2mg/kg x2 separated by 1-2 weeks​

    • Slightly higher rate of treatment failure than permethrin (14% vs 10%, resp) (39250129 ref 45)

    • Not for use in children <15kg

Pediatrics​

  • For <2 months, sulfur 5-10% ointment

  • For >2 months, permethrin

Decontamination​

  • Benefit of this is unknown/not well-studied.  Transmission via fomites is possible, but uncommon. 

  • Wash clothing and bedding in hot water, or seal in air tight bag for 3 days. 

Contacts

  • empiric treatment of close contacts should be given

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