Rash Illness Outbreaks at Child Care Facilities Associated with the White-Marked Tussock Moth Caterpillar, Hillsborough County, Florida, 2004 -2012

BACKGROUND:   The Hillsborough County Health Department (HCHD) in Tampa, FL, became aware of rash illnesses associated with caterpillar exposure after multiple child care facilities reported children with pruritic rashes on their arms, legs, and abdomen during the months of March and April in the successive years of 2004 and 2005.  Additionally, these caterpillar-associated child care outbreaks recurred at the same time of year in 2011 and 2012.  While, in general, the rashes did not cause severe morbidity, misdiagnosis and inappropriate treatment of these children was common.  Most of the affected children had direct contact with the caterpillars or their cocoons.

METHODS:   In March/April 2004, the HCHD Program investigated multiple outbreaks of rash illness of unknown etiology among child care attendees.  Physicians diagnosed the affected children with a wide range of conditions including: varicella, scabies, flea bites, mosquito bites, scarlet fever, fifth disease, contact dermatitis or nonspecific viral rash.  One year later, additional rash illness outbreaks at child care facilities were reported – including some of the same facilities that reported a problem the year before.  This prompted a thorough epidemiologic investigation with associated site visits.  Outbreak line lists were collected from all affected facilities.  The identical caterpillar was seen on the playgrounds of all of the affected child care facilities.  Digital photos were taken and emailed to an entomologist with the Florida Department of Agriculture and Consumer Services (DOACS).  A significant effort was made to inform our medical community and other county health departments (CHDs) around the state of these caterpillar associated rashes.

RESULTS:   Attack rates for the children at the affected child care facilities ranged from 12.6% to 21.7%.  The Florida DOACS entomologist identified the caterpillar as the white-marked tussock moth caterpillar.  Child care facilities were instructed to minimize contact between the children and the caterpillars.  In 2005, the HCHD was unable to identify other Florida CHDs experiencing caterpillar-associated rash outbreaks.  By 2012, numerous other CHDs in Florida were reporting the same phenomenon.

CONCLUSIONS:  When investigating rash outbreaks of unknown etiology among children, caterpillar-associated etiology should be considered.  Characteristics of these rash outbreaks include: 1) a mild pruritic rash on the abdomen, back, arms, or legs; 2) varied physician diagnoses; and 3) the presence of caterpillars and cocoons that have been associated with rashes.  Better awareness of caterpillar-associated outbreaks by medical and public health professionals will spare children unnecessary treatment or exclusion from child care or school.