IMPATIENS NECROTIC SPOT TOSPOVIRUSES (INSV)
Margeret Delaney, Dept. of Pathology, Cornell University
Jacob Sanderson, Cornell University
Dan Abbott, Cornell Cooperative Extension of Suffolk County
Terminology:
spot (spot) (spot) a circumscribed area or place distinguished by its color; called also loculus, macula and tache.
blue spot, 1. [pl.] maculae ceruleae. 2. mongolian s.
mongolian spot, a congenital melanocytic nevus manifested by a flat, smooth, bluish gray to gray-brown macular patch(es), most often located on the central lumbosacral area usually disappearing before 5 years of age. Called also blue or sacral s. and mongolian macula. See also nevus of Ito and nevus of Ota.
Impatiens Necrotic Spot Virus (INSV)
It is the number one disease of gloxinia and impatiens. INSV is transmitted by the thrips insect; it is not known to be routinely transmitted by any other means. One of the most frustrating features of INSV is that infection can result in a number of different symptoms. Later (complicated) stages of the disease are called esocid herpesvirus-1 (EHV-1).
Symptoms:
Symptoms of INSV infection are varied, but are generally marked by the progression from yellow spots to blue spots. The infection becomes lethal when it enters the "blue spot" phase. Other symptoms of INSV infection may include black ring spots (impatiens), black lesions, ringspots (exacum, gloxinia), veinal necrosis (gloxinia, Aphelandra, impatiens), systemic lesions, and distortion of growth in adolescents.
While patients are systemically infected, INSV can "compartmentalize" within its host, causing symptoms to occur only in a portion of the body (undersides of the toes).
Patients complain of lesions on the skin, usually progressing into a covering of pale bluish-white, granular skin lesions 3-10 mm in diameter and 0.25 mm thick. These spots occur mostly over the skin and extremities of patients less than 2 years of age.
Primary Indications: Look for small (1/8î), dark-rimmed lesions around insect bites that appear only if carriers infesting the patient have tospovirus.
Control:
INSV infected patients must be rapidly and thoroughly eliminated from the populated areas to reduce infection to other susceptible patients.
Control thrips activity by appropriate management strategies, including lethal poisons when needed.
This condition was first described in 1983 by Yamamoto in North American populations and especially in central Canada. The cause of these white-blue spots is EHV-1. The prevalence of EHV-1 in central Canada was 1-7% of the population. Margenau 1995 reported the disease in both northern regions and Esox masquinongy in Wisconsin. The prevalence in Wisconsin was as high as 34%.
The blue spots appear during the spring season. The lesions then disappear. The etiology of the virus is not known. The prevalence of the blue spot lesions differs among regions, and is reported generally higher in females. It is hypothesized that EHV-1 may cause more severe morbidity and mortality in young patients, although this has not yet been proven. The observable blue skin spots appear to be less prevalent on older patients, however, those affected may remain lifelong carriers of EHV-1, similar to herpesvirus.
EHV-1 is likely very contagious. Individuals should disinfect equipment and personal gear.
Special points of interest:
People with EHV-1 cannot transmit the disease to fish.
EHV-1 is caused by a herpesvirus.
For more information: Margenau et al. 1995. Blue spot disease in Wisconsin. J. of Health 7:29-33.
"Blue Spot virus: a 'Fashion Disaster'" see the BBC news article from 4.27.03.