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Caterpillar-Associated Rashes in Children — Hillsborough County, Florida, 2011

In March and April 2011, the Hillsborough County Health Department (HCHD) Epidemiology Department (Tampa, Florida) investigated three clusters of rash illness linked to the white-marked tussock moth caterpillar among persons at two child care centers and one elementary school. At least 23 children and one adult were affected; most had direct contact with caterpillars. HCHD provided recommendations on treatment and preventing caterpillar exposure to the three facilities, health-care providers, and local agencies, and through local news media. Child care centers and elementary schools in Hillsborough County previously have experienced caterpillar-associated rash outbreaks in 2004 and 2005 (1). Awareness of this problem, particularly during periods of caterpillar infestation, can minimize morbidity and help to avoid inappropriate diagnoses and treatment by health-care providers.

On March 30, 2011, a local elementary school in Hillsborough County reported a cluster of rash illnesses to HCHD. Among the initial four cases of rash, one child received a diagnosis of molluscum contagiosum, one of viral rash, and two siblings received a diagnosis of varicella. All four children had received the recommended 2 doses of varicella vaccine. By April 6, an additional eight cases of a mild pruritic rash were reported among children at the school. No systemic signs of illness, such as fever, were reported. Because caterpillar-associated rash outbreaks had occurred in previous years, the school nurse was asked about potential exposure to caterpillars or other environmental factors that could cause contact dermatitis among the children, but none were reported.

On April 5, a second rash illness cluster was reported to HCHD by a local child care facility located within 2 miles of the elementary school. The facility reported a mild pruritic rash in three of 34 children and one of three staff members, all with an onset of April 5. The affected staff member had a history of allergic reactions. When asked if caterpillars were present around the facility, the director said the caterpillars were so numerous that staff members had stopped allowing the children on the playground. The description of the caterpillars was consistent with the white-marked tussock moth caterpillar (Orgyia leucostigma) (Figure), which ranges through much of the eastern United States and as far west as Texas and Colorado. The facility was advised to notify parents of affected children about the caterpillars so that they could discuss this with their child's pediatrician as the potential cause of rash. On April 6, epidemiologists conducted a field visit to the affected elementary school and child care facility to determine the type of caterpillars present and the extent of contact between the children and the caterpillars. White-marked tussock moth caterpillars and their cocoons were observed on the trees and playground equipment at both sites and at the front entrance of the child care facility.

On April 7, 2011, another child care facility called to inquire about recommendations for preventing the spread of methicillin-resistant Staphylococcus aureus (MRSA). A child had been clinically diagnosed with MRSA folliculitis and treated with antibiotics. However, no pustules were noted, and no testing was performed. When asked, the director of the child care facility said the center's playground had been infested with caterpillars the previous week. The affected child reportedly had captured a caterpillar from the facility playground and likely had touched the caterpillar. Her pruritic rash was located on her abdomen. An additional seven children in the facility also experienced pruritic rashes on their abdomens. HCHD again recommended preventing contact between children and caterpillars. In addition, basic MRSA education was provided, and a request was made that any child testing positive for MRSA be reported to the HCHD epidemiology program.

For the three facilities experiencing outbreaks of rash illnesses in 2011, recommendations included 1) preventing contact between the children and caterpillars or cocoons, 2) notifying parents of the risks associated with caterpillar exposure, and 3) power-washing playground equipment to remove the caterpillars, cocoons, and their hairs. HCHD also implemented a strategy to notify the community and health-care providers about the risks for caterpillar- and cocoon-related illness. Informational sheets with pictures of the caterpillars and basic prevention messages were distributed to the school district, child care licensing, and county Head Start program offices. Interviews with local media were conducted advising the public to avoid contact with caterpillars and cocoons. Information describing the caterpillar and typical symptoms associated with exposure was provided to health-care providers directly by fax and distributed in the HCHD epidemiology department newsletter. The local agriculture extension office also was notified of the situation.

Reported by

David Atrubin, MPH, Lea Wansbrough, MPH, Kelly Cruse, MPH, CHES, Danielle Stanek, DVM, Carina Blackmore, DVM, PhD, Florida Dept of Health. Corresponding contributor: Carina Blackmore,, 850-245-4732.

Editorial Note

The 2011 clusters of caterpillar- and cocoon-associated dermatitis follow the pattern of similar outbreaks at child care facilities that were investigated in Hillsborough County in the spring of 2004 and 2005 (1). The association between caterpillars and rash became apparent in 2005, when HCHD observed that three child care facilities had reported rash outbreaks during April of successive years. Attack rates for rash among children at the three facilities ranged from 12.6% to 21.7%. The affected children did not experience an immediate reaction, but rather a self-limiting pruritic, papular rash with distribution on the abdomen, chest, back, arms, or legs. Physical contact with the caterpillars was reported by almost all of the children experiencing a rash illness. Area physicians variously diagnosed the children as suffering from varicella, scabies, flea bites, mosquito bites, scarlet fever, fifth disease, contact dermatitis, or nonspecific viral rash. As a result of these misdiagnoses, the children often were treated inappropriately and excluded from child care unnecessarily. An entomologist for the Florida Department of Agriculture and Consumer Services identified the caterpillar associated with the 2005 rash outbreak as the white-marked tussock moth larva/caterpillar (O. leucostigma). He reported that this caterpillar can cause contact dermatitis and that it previously had been linked to rash outbreaks in the state.

The scientific literature clearly documents the ability of tussock moth caterpillars to cause rashes after physical contact. These include accounts of seven persons who developed rashes after handling the white-marked tussock moth caterpillar in Minnesota in 1921 (O. leucostigma) (2). In 2000, the Douglas-fir tussock moth caterpillar (Orgyia pseudotsugata) was the cause of rash illnesses in Boy Scouts at a summer camp in New Mexico (3).

The pathologic mechanism of caterpillar-associated rash is not understood entirely and depends on the caterpillar species. The mechanism is thought to involve exposure to chemicals on caterpillar or cocoon hairs (spicules) or mechanical irritation (4). Contact with hairs on the body and cocoon of the white-marked tussock moth caterpillars appears to cause skin irritation. Additionally, when caterpillars and cocoons are in high density, particularly susceptible persons can develop a rash when the hairs become airborne. In these situations, the rash might not occur on the area of the skin where caterpillar or cocoon contact occurred; several children at the Florida facilities had rash on the abdomen and back.

Several other types of stinging caterpillars are common in Florida, including the io moth caterpillar (Automeris io), the saddleback caterpillar (Sibine stimulea), and the puss caterpillar (Megalopyge opercularis) (5). Contact with these caterpillars often will cause a more severe sting for which the pain will be apparent immediately to the victim. In contrast, the white-marked tussock moth produces delayed, minor irritation (2). Time from exposure to onset of rash is likely minutes to hours, similar to the onset time reported after exposure to other species of tussock moths. Treatment recommendations include placing adhesive tape over the affected area and repeatedly stripping the tape off to help remove the tiny hairs, washing the area with soap and water, applying ice packs to reduce the stinging sensation, and applying a topical, low potency steroid cream (4). If the eyes are involved; the person has a history of hay fever, asthma, or allergies; or allergic reactions develop, a health-care provider should be contacted.

In light of these outbreaks, exposure to caterpillars and their cocoons should be considered when investigating rash illness outbreaks of unknown etiology during times of the year when the insect larvae are common. Factors that raise suspicion of a caterpillar-cocoon–associated outbreak, especially among children, include 1) mild pruritic rash on the abdomen, chest, back, arms, or legs that is not accompanied by fever; 2) pruritic rash outbreaks that have varied physician diagnoses; and 3) most importantly, the presence of caterpillars and cocoons known to cause pruritic rash combined with the opportunity for exposure.


Tom Loyless, Florida Dept of Agriculture and Consumer Svcs.


  1. Cruse K, Atrubin D, Loyless T. Rash illness outbreaks at daycare facilities associated with the tussock moth caterpillar, April 2004 and April 2005. Florida J Environ Health 2007;195:14–7.
  2. Knight HH. Observations on the poisonous nature of the white-marked tussock moth. J Parisitology 1922;8:133–5.
  3. Redd JT, Vorhees RE, Torok TJ. Outbreak of lepidopterism at a Boy Scout camp. J Am Acad Dermatol 2007;56:952–5.
  4. Goodard J. Physician's guide to arthropods of medical importance. 5th ed. Boca Raton, FL: CRC Press; 2007:57–9.
  5. Heppner JB. Urticating caterpillars in Florida: 1 io moth, Automeris io (Lepidoptera: Saturniidea). Entomology circular no. 362. Gainesville, FL: Florida Department of Agriculture and Consumer Services; 1994. Available at Accessed March 21, 2012.

What is already known on this topic?

Persons who have direct contact with certain types of caterpillars or who visit areas infested with caterpillars or their cocoons can develop rash.

What is added by this report?

Multiple rash illness outbreaks among at least 23 children and one adult in Hillsborough County, Florida, were associated with exposure to the white-marked tussock moth caterpillar. Because of the frequent misdiagnoses of these rashes, children often are treated and excluded from child care or school inappropriately.

What are the implications for public health practice?

Public health professionals can help improve the diagnosis and treatment of caterpillar-associated rashes by educating child care facilities, schools, and health-care providers about this health risk. Educational efforts also should focus on strategies to limit exposure to the insects and their toxic hairs.

FIGURE. White-marked tussock moth caterpillar (Orgyia leucostigma)

The figure shows a white-marked tussock moth caterpillar (Orgyia leucostigma, which ranges through much of the eastern United States and as far west as Texas and Colorado.

Photo/David Atrubin, Florida Department of Health

Alternate Text: The figure above shows a white-marked tussock moth caterpillar (Orgyia leucostigma, which ranges through much of the eastern United States and as far west as Texas and Colorado.

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