Como destruir fomites?

Published in Dermatology

Journal Scan / Research · January 02, 2020

Eliminating Scabies Parasites From Fomites

Journal of the American Academy of Dermatology

TAKE-HOME MESSAGE

• Over 5500 adult mites and 2300 eggs of S. scabiei were obtained from a porcine model (which is indistinguishable from human scabies) and used in an ex vivo experiment to determine ways to eliminate scabies. Thermal killing (ie, 100% of scabies mites and eggs dead) at ≥50°C (for at least 10 minutes) and freezing below −10°C (for at least 5 hours) was effective. Washing or heat-drying beyond the heat threshold in conventional machines killed parasites quickly. Detergent or ozone laundry disinfection had minimal effect on mite and egg mortality. If there is no access to washer/dryer or freezer, scabies-contaminated fomites may be isolated in plastic bags until all parasites are dead, which may take up to 3 days in temperate–dry and 8 days in warm–humid conditions.

• In this labor-intensive experiment, the authors for the first time validated "real-life" decontamination modalities for scabies, which may be applicable in settings with and without electricity. Environmental decontamination should always be integrated with pharmaceutical therapy.

– InYoung Kim, MD, PhD

 Dermatology

Written by

 

 

Scott A Norton MD, MPH, MSc

The word, scabies, refers to both the mites, scientifically known as Sarcoptes scabiei, and the skin condition that it causes. Scabies, in both senses of the word, is associated with discomfort, fear, anxiety, revulsion, and myth. Many of the myths center on how infectious an individual who has scabies is—and how one actually acquires the infestation. A lingering issue is whether scabies is reliably transmitted via fomites (inanimate objects such as clothing and bed linens). A corollary question is: How can one decontaminate clothing and bed linens that have been used by scabies-infested people?

Protocols that address community-level detection, treatment, control, prevention, and decontamination appear in infection-control manuals for hospitals, nursing homes, prisons and other confined facilities, daycare centers, and school systems. Most protocols assume access to simple resources, such as electricity, water, and replacement items. However, many places with scabies hyperinfestation lack the necessary resources (ie, water, power, laundry appliances, heat source) to follow such guidelines.

Thus, the investigation reported in this study was prompted, in part, by an inquiry from indigenous Australian communities in remote Queensland. There, scabies infestation is hyperendemic and health consequences are far more serious than mere incessant, unremitting, intractable, generalized pruritus.

Bernigaud and colleagues from France, Australia, and Sri Lanka conducted simple studies using thousands of mites and eggs collected from porcine models (ie, scabies-infested pigs maintained in laboratory conditions). The studies were conducted on ex vivo mites and eggs (those that were no longer on the living host).

Their study is unique in that they looked at viability of scabies eggs, something that is important in a discussion of fomite-based transmission but has never been done before. They tested dozens of ways to decontaminate fomite-laden fabrics, and they provide us an evidence-based algorithm for conducting chemical-free decontamination based on physical factors such as temperature and humidity.

One of their references is the classic paper by Kenneth Mellanby, an entomologist in the United Kingdom during World War II.1 As Allied military forces gathered in close quarters, crowded conditions prompted great concern for outbreaks of scabies. One should read Mellanby's 1941 paper, "The transmission of Scabies," published in the British Medical Journal. The paper describes that "the volunteers were all pacifists who had offered to co-operate in this work and…agreed to submit themselves to infection [with scabies] and to allow the course of the disease to be followed on their person…. Uninfected volunteers slept together in the same beds as these men suffering from scabies…for seven nights…. The men were stripped and inspected daily for a period of about a month (sometimes longer)…." Mellanby examined thousands of patients during the course of his experiments—and his various papers are the basis of much of our knowledge of this nearly universal affliction.

Reference

1. Mellanby K. Transmission of scabies. Br Med J. 1941 Sep 20;2(4211):405-406. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2284263/pdf/brmedj03939-0015.pdf

Abstract

Scabies is one of the most prevalent infectious dermatological diseases worldwide. Overcrowding, high population movement and suboptimal health care are major risk factors for outbreaks, particularly in disadvantaged populations and institutional settings. In the tropics scabies often causes secondary bacterial infections and potentially life threatening sequelae including sepsis, glomerulonephritis, rheumatic fever and heart disease. Direct skin-to-skin contact is the main transmission pathway, however, as mites survive short-term outside their host, contaminated fomites can also spread the disease, especially in the cases of profuse or crusted scabies. Parasites within skin squames shed into beddings have been reported to infect laundry workers, and have been responsible for therapeutic failure. Consequently, environmental decontamination should be integrated with individual medication. To date, no field studies have been performed to validate decontamination measures. As there is no in vitro culture, previous experimental research was limited in parasite numbers and never considered the egg stage. Accordingly, the existing decontamination protocols are based on poor statistical power and vary significantly, resulting in confusion of patients and medical workers. We aimed to generate statistically valid experimental data as a basis to develop standardized guidelines with clear and simple directions for scabies outbreaks.

Journal of the American Academy of Dermatology

How to Eliminate Scabies Parasites From Fomites — A High Throughput Ex Vivo Experimental Study

J Am Acad Dermatol 2019 Dec 16;[EPub Ahead of Print], C Bernigaud, DD Fernando, H Lu, S Taylor, G Hartel, O Chosidow, K Fischer 

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Benjamin Hidalgo-Matlock
Skin Care Physicians of Costa Rica

Clinica Victoria en San Pedro: 4000-1054
Momentum Escazu: 2101-9574

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