Western equine encephalomyelitis virus infection affects the life table characteristics of Culex tarsalis (Diptera: Culicidae)

The life table attributes of Culex tarsalis Coquillett females infected experimentally by feeding on 4 and 6 log10 plaque-forming units (PFU) of western equine encephalomyelitis virus (WEEV) per milliliter of heparinized chicken blood were compared with an uninfected control group. Females continually were offered 10% sucrose and an oviposition substrate and daily a blood meal through a biomembrane feeder. Mortality (dead females) and fecundity (female eggs per female) were monitored daily until all females died. Overall, 94% of 198 females in the two virus-infected groups were positive for WEEV at death when tested by plaque assay; the average body virus titer at death did not differ between groups. WEEV infection significantly altered the life table characteristics of Cx. tarsalis. Life expectancy at infection in days (ex), reproductive effort in female eggs per female per generation (Ro), and generation time (T) in days for the infected cohorts were significantly lower than for the uninfected controls, whereas the reproductive rate (rc) in female eggs per female per day was higher for infected than uninfected cohorts. In agreement with the WEEV infection data that showed similar body titers, there were few differences between the life table parameters for the 4 and 6 log10 PFU treatment groups. Greatest differences were observed for survivorship between days 17-40 when virus titers in infected dying females were greatest. Our data extend recent studies that indicate mosquito infection with encephalitis viruses has a cost of reduced life expectancy and fitness.     

Persistence and amplification of St. Louis encephalitis virus in the Coachella Valley of California, 2000-2001

The introduction of a St. Louis encephalitis virus (SLE) genotype new to southeastern California during 2000 was followed by focal enzootic amplification in the Coachella Valley that was detected by seroconversions of 29 sentinel chickens in five of nine flocks of 10 chickens each, isolations of virus from 30 of 538 pools of 50 Culex tarsalis Coquillett females, and collection of 30 positive sera from 2,205 wild birds. This SLE strain over wintered successfully and then amplified during the summer of 2001, with 47 sentinel seroconversions in eight of nine flocks, 70 virus isolations from 719 pools of Cx. tarsalis and Cx. p. quinquefasciatus Say, and 40 positive sera from 847 wild birds. Human illness was not detected by passive case surveillance, despite issuance of a health alert during 2001. Virus amplification during both years was associated with above average temperatures conducive for extrinsic incubation and below average precipitation during spring associated with below average vector abundance. Seroconversions by sentinel chickens provided the timely detection of virus activity, with initial conversions detected before positive mosquito pools or wild bird infections. Vertical infection was not detected among Cx. tarsalis adults reared from immatures collected during the fall-winter of 2000, even though SLE over wintered successfully in this area. Early seroconversions by a sentinel chicken during February 2001 and a recaptured Gambel's quail in April 2001 provided evidence for transmission during winter and spring when ambient temperatures averaged below 17 degrees C, the threshold for SLE replication.     

Recurrent Primary Cardiac Lymphoma on Aortic Valve Allograft: Implications for Therapy

Primary malignant cardiac lymphomas associated with grafts are extremely rare: to our knowledge, only 6 cases of prosthesis-associated B-cell lymphoma have been reported. Ours is the first report of recurrent diffuse large B-cell lymphoma associated with aortic valve allografts.We treated a 60-year-old man who presented in early 2007 with aortic valve endocarditis. He underwent aortic valve replacement with an allograft; the resected native valve showed active endocarditis without tumor. In January 2011, the patient underwent repeat aortic valve replacement because of symptomatic aortic regurgitation. The explanted valve specimen displayed diffuse large B-cell lymphoma. In September 2011, the patient presented with fever and a mass around the aortic valve. He died in January 2012. On autopsy, the explanted replacement valve displayed recurrent diffuse large B-cell lymphoma. The recurrent lymphoma on a new graft leads us to believe that this tumor is more aggressive than had been thought. We propose early systemic chemotherapy, in addition to tumor resection, for the possibility of a better prognosis. We discuss our patient''s case and review the relevant medical literature.     

Magnetic Resonance Imaging in the Diagnosis of Temporomandibular Disorders with a Report of Two Cases

Magnetic resonance imaging for the temporomandibular joint has moved from an experimental stage to a routine procedure at some institutions. The use of this technique for evaluation of the joint will increase as more institutions acquire this new diagnostic device. Magnetic resonance imaging has some unique properties that provide data unavailable by conventional imaging methods. An improved technique of magnetic resonance imaging is the use of the surface coil which greatly increases the detail and diagnostic accuracy. In addition to the surface coil, we have used a number of pulse sequences to better characterize the tissues.

Two cases of the use of magnetic resonance imaging in the evaluation of temporomandibular joint disorders are described in this paper. Surgical confirmation, arthrographic, and tomographic findings were available. Magnetic resonance imaging was used to image the interarticular disk and surrounding joint structures, and to provide pathophysiologic information on the tissues.     

High Throughput Quantitative Colorimetric Microneutralization Assay for the Confirmation and Differentiation of West Nile Virus and St. Louis Encephalitis Virus

An automated colorimetric micro-neutralization assay (CmNt) was developed for confirmation and differentiation of West Nile Virus (WNV)-positive human sera as a higher throughput alternative to the standard six-well plaque-reduction neutralization test (PRNT). CmNt was performed in high-capacity 96-well micro-titer plates and required 4–6 days to complete. Inhibition of infection was determined by reduced neutral red-dye retention and conveniently recorded by a colorimetric plate reader. Human sera previously confirmed by PRNT as either negative (N = 52), WNV positive (N = 81), or St. Louis encephalitis virus positive (N = 12) were tested by CmNt; interpreted results were virtually identical to PRNT with a reduced turnaround time and higher throughput. Additionally, a handful of dengue virus positive and negative specimens (four each) were tested by CmNt; interpreted results were identical to PRNT.     

Response of house finches to infection with sympatric and allopatric strains of western equine encephalomyelitis and St. Louis encephalitis viruses from California

Adult house finches from Kern County were inoculated subcutaneously with recent sympatric and allopatric isolates of western equine encephalomyelitis and St. Louis encephalitis (SLE) viruses made from Culex tarsalis Coquillett collected in Kern County and Coachella Valley, CA, respectively. Virulence, as measured by the amplitude of the viremia response during days 1 and 2 postinfection, varied significantly among strains, but independently of geographic origin. The intensity of the immune response, as measured by an enzyme immunoassay and a plaque reduction neutralization test, seemed to be independent of virulence, especially for SLE where some strains failed to produce a detectable viremia but elicited a strong antibody response. Our preliminary data indicated that strain virulence may be associated with the level of enzootic activity during the year of isolation.