Updates-By Carol A. Kemper, MD, FACP

Cases of Lyme Disease Remain Elevated

Sources: MMWR Morb Mortal Wkly Rep. 2001;50:181-185; Parola P, Raoult D. Clin Infect Dis. 2001;32:897-928.

As suburban sprawl pushes communities deeper into wooded areas, cases of Lyme disease in the United States have risen. Overall, 16,801 and 16,273 cases were reported to the CDC in 1998 and 1999, respectively, up 27-30% from 1997 and more than double the figures for 1990. Nine states accounted for 90% of cases, including (in descending order) Connecticut, Rhode Island, New York, Pennsylvania, Delaware, New Jersey, Maryland, Massachusetts, and Wisconsin. Disease incidence exceeded 100 cases per 100,000 population in 24 counties located in these states.

The highest disease incidence (950.7) was reported in Nantucket County, Mass. Only 139 cases were reported from California, one of which I know to have been imported from Wisconsin (Kemper CA. Infectious Disease Alert 2001;20:77-79). Five states reported no cases (Alaska, Georgia, Hawaii, Montana, and South Dakota). More than half of the cases were reported in June and July.

Lyme disease can generally be prevented with a few simple measures. Growing up in Minnesota, we were trained at an early age to observe good tick practices: 1) Avoid tick-prone areas, or if you must camp or hike in an area with ticks, wear long sleeved shirts and long pants with socks rolled up over the cuffs; 2) Use insect repellant; 3) Do a tick check every night before bed during peak season—check all hairlines, and around breasts and under arms where the skin is soft and warm; 4) Remove any tick within 24 hours of attachment in order to reduce the risk of transmission; and 5) check your pets before letting them back in the house.

People living in areas of greatest risk should consider vaccination. But vaccination is no substitute for good tick practices. Primary care physicians in endemic areas should consider posting recommendations for good tick practices in their waiting rooms, especially during spring and summer months.

Superinfection During Treatment of Otitis Media

Source: Dagan R, et al. J Infect Dis. 2001;183:880-886.

Dagan and associates prospectively examined whether cases of clinically refractory acute otitis media (AOM) are caused by superinfection with resistant organisms during antimicrobial therapy. Dagan et al examined 119 youngsters with AOM of < 7 days duration with positive cultures of middle ear fluid (MEF) for > 1 bacterial organism and > 1 nasopharyngeal culture (NP) for Streptococcus pneumonia (SP) obtained prior to the administration of antibiotics. Patients were assigned to receive azithromycin, amoxacillin-clavulanate, or trimethoprim-sulfamethoxazole. Repeat tympanocentesis for culture was performed at 4-6 days of therapy and in the event of relapse.

About one-third of the children reported 3 or more episodes of AOM in the past year and 24% had received antibiotics within the preceding month. H influenzae was isolated from 58% of patients, SP from 36%, and both organisms were isolated from 24%. About two-thirds of SP isolates from MEF and NP were susceptible to the agent received. Patients with positive NP cultures for SP were more likely to have positive MEF cultures for SP. A resistant MEF strain of SP was obtained from 13 of 32 children (41%) with a resistant NP SP strain, in contrast to only 3 of 57 (5%) children with a sensitive NP strain and 3 of 30 (10%) of children with negative NP cultures for SP. In 19 of 119 (16%) cases, an organism susceptible to the agent received was isolated from the MEF but NP cultures yielded resistant SP.

Within a few days of treatment, repeat MEF cultures demonstrated that the resistant SP strain had replaced the previous organisms in the MEF in 9 of these 19 patients (47%). In two cases, resistant SP replaced sensitive strains of SP, as demonstrated by strain type and anabiograms. Several of these children had shown initial improvement but then later relapsed.

Pediatricians and primary care physicians should be aware that clinically unresponsive otitis or relapse may be due to acquisition of resistant strains that had previously colonized the nasopharynx. It may be interesting to examine whether attempts at decolonization of nasopharyngeal carriage of resistant SP is beneficial.

Rotavirus Vaccine and Intussusception

Source: Murphy TV, et al. N Engl J Med. 2001;344:564-572.

Following 9 reports of intussusception in infants possibly related to vaccine use, rotavirus vaccine was pulled from the market in 1999 (Kemper CA. Infectious Disease Alert 1999;21: 168). This investigation of vaccinated infants confirms that rotavirus vaccine, for reasons that are not clear, does indeed increase the risk of intussusception. Of 426 infants with intussusception, 74 (17.4%) had received rotavirus vaccine. Compared with infants who did not receive rotavirus vaccine, vaccinated infants were at 14 times greater risk of intussusception during the first week post-vaccination. Of note, during the initial clinical trials performed for licensing, only 5 cases of intussusception occurred in more than 10,000 infants.