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journal articleBiomedical Informatic

High costs of infection: Alphavirus infection reduces digestive function and bone and feather growth in nestling house sparrows (Passer domesticus).

Increasingly, ecoimmunology studies aim to use relevant pathogen exposure to examine the impacts of infection on physiological processes in wild animals. Alphaviruses are arthropod-borne, single-stranded RNA (ssRNA) viruses ("arboviruses") responsible for millions of cases of human illnesses each year. Buggy Creek virus (BCRV) is a unique alphavirus that is transmitted by a cimicid insect, the swallow bug, and is amplified in two avian species: the house sparrow (Passer domesticus) and the cliff swallow (Petrochelidon pyrrhonota). BCRV, like many alphaviruses, exhibits age-dependent susceptibility where the young are most susceptible to developing disease and exhibit a high mortality rate. However, alphavirus disease etiology in nestling birds is unknown. In this study, we infected nestling house sparrows with Buggy Creek virus and measured virological, pathological, growth, and digestive parameters following infection. Buggy Creek virus caused severe encephalitis in all infected nestlings, and the peak viral concentration in brain tissue was over 34 times greater than any other tissue. Growth, tissue development, and digestive function were all significantly impaired during BCRV infection. However, based on histopathological analysis performed, this impairment does not appear to be the result of direct tissue damage by the virus, but likely caused by encephalitis and neuronal invasion and impairment of the central nervous system. This is the first study to examine the course of alphavirus diseases in nestling birds and these results will improve our understanding of age-dependent infections of alphaviruses in vertebrate hosts

High costs of infection: Alphavirus infection reduces digestive function and bone and feather growth in nestling house sparrows (<i>Passer domesticus</i>) - Fig 6

<p><b>Intestinal (A) aminopeptidase-N and (B) maltase activities during infection (mean ± SEM).</b> Nestlings were age 7 days post-hatch when infected (0 DPI). N = 4 per group. Data were analyzed by two-way ANOVA.</p

Viral load (mean ± SEM PFU BCRV/mg tissue) in tissues of BCRV-infected birds.

<p>N = 4 per sample type and DPI.</p

High costs of infection: Alphavirus infection reduces digestive function and bone and feather growth in nestling house sparrows (<i>Passer domesticus</i>) - Fig 4

<p><b>Apparent assimilable mass coefficient (a) and excreta lipid content (B) during infection (mean ± SEM).</b> Nestlings were age 7 days post-hatch when infected (0 DPI). n = 11–12 at 0-1DPI; n = 8 at 2DPI; n = 4 at 3DPI. Asterisks above bars indicate significant difference between treatment groups by two-sample t-test (3 DPI was not statistically analyzed due to low sample size).</p

Brain sample of a nestling house sparrow infected with BCRV.

<p>Mild lymphoplasmacytic cuffing and perivascular edema, cerebrum. Several shrunken, deeply eosinophilic, necrotic neurons are present in the vicinity of the affected blood vessel (arrows).</p

Clinical and molecular epidemiology of invasive Staphylococcus aureus infection in Utah children; continued dominance of MSSA over MRSA.

BackgroundInvasive Staphylococcus aureus infections are a common cause of morbidity and mortality in children. In the early 2000's the proportion of infections due the methicillin-resistant S. aureus (MRSA) increased rapidly. We described the clinical and molecular epidemiology of invasive S. aureus disease in a pediatric population.MethodsWe prospectively identified children in Utah with invasive S. aureus infections. Medical records were reviewed to determine diagnosis and clinical characteristics. Isolates were genotyped using multi-locus sequence typing. The presence of genes encoding the Panton-Valentine leukocidin (PVL) was determined using polymerase chain reaction.ResultsOver a 4-year period between January 2009 and December 2012, we identified 357 children, hospitalized at Primary Children's Hospital, with invasive S. aureus infections and isolates available for the study. Methicillin-susceptible S. aureus (MSSA) caused 79% of disease, while MRSA caused only 21% of disease. Mortality associated with invasive S. aureus infection was 3.6%. The most common diagnoses were osteoarticular infections (38%) followed by central line associated blood stream infections (19%) and pneumonia (12%). We identified 41 multi-locus sequence types. The majority of isolates belonged to 6 predominant clonal complexes (CC5, CC8, CC15, CC30, CC45, CC59). PVL was present in a minority (16%) of isolates, of which most were ST8 MRSA.ConclusionsMSSA was the primary cause of invasive S. aureus infections at our institution throughout the study period. A limited number of predominant strains accounted for the majority of invasive disease. The classic virulence factor PVL was uncommon in MSSA isolates. Further study is needed to improve our understanding of S. aureus virulence and disease pathogenesis