EHDV-2 Infection Prevalence Varies in Culicoides sonorensis after Feeding on Infected White-Tailed Deer over the Course of Viremia

Epizootic hemorrhagic disease viruses (EHDVs) are arboviral pathogens of white-tailed deer and other wild and domestic ruminants in North America. Transmitted by various species of Culicoides, EHDVs circulate wherever competent vectors and susceptible ruminant host populations co-exist. The impact of variation in the level and duration of EHDV viremia in white-tailed deer (Odocoileus virginianus) on Culicoides infection prevalence is not well characterized. Here we examined how infection prevalence in a confirmed North American vector of EHDV-2 (Culicoides sonorensis) varies in response to fluctuations in deer viremia. To accomplish this, five white-tailed deer were experimentally infected with EHDV-2 and colonized C. sonorensis were allowed to feed on deer at 3, 5, 7, 10, 12, 14, 18, and 24 days post infection (dpi). Viremia profiles in deer were determined by virus isolation and titration at the same time points. Blood-fed Culicoides were assayed for virus after a 10-day incubation (27 ◦C) period. We found that increases in deer EHDV blood titers significantly increased both the likelihood that midges would successfully acquire EHDV and the proportion of midges that reached the titer threshold for transmission competence. Unexpectedly, we identified four infected midge samples (three individuals and one pool) after feeding on one deer 18 and 24 dpi, when viremia was no longer detectable by virus isolation. The ability of ruminants with low-titer viremia to serve as a source of EHDV for blood-feeding Culicoides should be explored further to better understand its potential epidemiological significance

HbA1c Test as a Tool in the Diagnosis of Gestational Diabetes Mellitus.

Gestational diabetes mellitus (GDM) is a prevalent and potentially serious condition which may put both mothers and neonates at risk. The current recommendation for diagnosis is the oral glucose tolerance test (OGTT). This study aimed to determine the usefulness of HbA1c test as a diagnostic tool for GDM as compared to the traditional criteria based on the OGTT.This was a diagnostic test accuracy study. We performed OGTT and HbA1c test in women attending prenatal visits at a tertiary hospital. GDM was defined according to WHO1999 or ADA/WHO 2013 criteria. ROC curve was used to evaluate the diagnostic performance of HbA1c. Sensitivity, specificity and likelihood ratios for different HbA1c cut-off points were calculated.Of the 262 women in the third trimester of gestation enrolled in the study, 86 (33%) were diagnosed with GDM. Only five of these women presented HbA1c ≥48 mmol/mol (6.5%). This cut-off point presented 100% specificity but very low sensitivity (7%). Based on ROC curve, and considering OGTT as the reference criterion, HbA1c ≥40 mmol/mol (5.8%) showed adequate specificity in diagnosing GDM (94.9%) but low sensitivity (26.4%). Unlike, HbA1c values of 31 mmol/mol (5.0%) presented adequate sensitivity (89.7%) but low specificity (32.6%) to detect GDM. For women with HbA1c ≥40 mmol/mol (5.8%), the positive and negative likelihood ratios were 5.14 (95%CI 2.49-10.63) and 0.78 (0.68-0.88), respectively. The post-test probability of GDM was about 40%, representing a 4.0-fold increase in the mean pre-test probability. This cut-off point could eliminate the need for the unpleasant and laborious OGTT tests in almost one third of cases, as 38% of patients with GDM may be diagnosable by HbA1c test alone.Our results show that combined HbA1c and OGTT measurements may be useful in diagnosing GDM

HbA1c test performance in diagnosing GDM.

<p>LR+ = positive likelihood ratio; LR− = negative likelihood ratio. N = 262, WHO 1999 and/or ADA/WHO 2013 reference criteria.</p><p>HbA1c test performance in diagnosing GDM.</p

Fagan´s Nomogram for the HbA1c test showing post-test probabilities of gestational diabetes in pregnant women with HbA1c ≤31 mmol/mol (5.0%) and HbA1c ≥40 mmol/mol (5.8%).

<p>Fagan´s Nomogram for the HbA1c test showing post-test probabilities of gestational diabetes in pregnant women with HbA1c ≤31 mmol/mol (5.0%) and HbA1c ≥40 mmol/mol (5.8%).</p

ROC curve for HbA1c values in diagnosing GDM.

<p>Blue Line—HbA1c <i>vs</i> WHO 1999 N = 262, Red line—HbA1c <i>vs</i> ADA/WHO 2013* N = 142. * After June 2011.</p

Study Design.

<p>Study Design.</p

Clinical and laboratory characteristics of pregnant women with and without GDM, according to WHO 1999 or ADA/WHO 2013^a diagnostic criteria.

<p>^a After June 2011.</p><p>Data are mean ± SD, except for FHDM, PHGDM and PHHT. GDM = gestational diabetes mellitus, OGTT = oral glucose tolerance test, BMI = body mass index, SBP = systolic blood pressure, DBP = diastolic blood pressure, FG = fasting glycemia, 1hG = glycemia after 1h of glucose load, 2hG = glycemia 2h after glucose load, Hb = haemoglobin, FHDM = family history of DM, PHDMG = previous history of GDM, PHHT = previous history of hypertension.</p><p>Clinical and laboratory characteristics of pregnant women with and without GDM, according to WHO 1999 or ADA/WHO 2013<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135989#t001fn001" target="_blank">^a</a> diagnostic criteria.</p

EHDV-2 Infection Prevalence Varies in <i>Culicoides sonorensis</i> after Feeding on Infected White-Tailed Deer over the Course of Viremia

Epizootic hemorrhagic disease viruses (EHDVs) are arboviral pathogens of white-tailed deer and other wild and domestic ruminants in North America. Transmitted by various species of Culicoides, EHDVs circulate wherever competent vectors and susceptible ruminant host populations co-exist. The impact of variation in the level and duration of EHDV viremia in white-tailed deer (Odocoileus virginianus) on Culicoides infection prevalence is not well characterized. Here we examined how infection prevalence in a confirmed North American vector of EHDV-2 (Culicoides sonorensis) varies in response to fluctuations in deer viremia. To accomplish this, five white-tailed deer were experimentally infected with EHDV-2 and colonized C. sonorensis were allowed to feed on deer at 3, 5, 7, 10, 12, 14, 18, and 24 days post infection (dpi). Viremia profiles in deer were determined by virus isolation and titration at the same time points. Blood-fed Culicoides were assayed for virus after a 10-day incubation (27 &#176;C) period. We found that increases in deer EHDV blood titers significantly increased both the likelihood that midges would successfully acquire EHDV and the proportion of midges that reached the titer threshold for transmission competence. Unexpectedly, we identified four infected midge samples (three individuals and one pool) after feeding on one deer 18 and 24 dpi, when viremia was no longer detectable by virus isolation. The ability of ruminants with low-titer viremia to serve as a source of EHDV for blood-feeding Culicoides should be explored further to better understand its potential epidemiological significance