Hematological survey of common neotropical bat species from Costa Rica

Although bats are one of the largest groups within the class Mammalia and may carry several zoonotic diseases, basic information about their hematology is limited. In this study, hematocrit (Hct), total white blood cell counts (TWBC; leukocytes), and differential white blood cell counts (DWBC) of free-ranging Neotropical bats were quantified. Blood samples from 255 bats representing 26 species from the families of Emballonuridae (3 species; 33 individuals), Molossidae (2 species; 26 individuals), Mormoopidae (1 species; 1 individual), Phyllostomidae (18 species; 180 individuals), and Vespertilionidae (2 species; 15 individuals) were collected in a Caribbean lowland rainforest of Costa Rica. Hct was measured after centrifugation of microhematocrit capillaries, TWBCs were performed using the Unopette system and a hemocytometer, and DWBCs were performed on eosin methylene blue stained blood films. Hct of bats ranged between 51.8 +/- 0.7% for Phyllostomus discolor (n = 27) and 65.8 +/- 2.2% for Molossus sinaloae (n = 6). Bat species of the same taxonomic family had comparable TWBCs; these were lower for insectivorous emballonurid, molossid, and vespertilionid bat species than for mostly phytophagous phyllostomid bat species. However, Ectophylla alba (Phyllostomidae) exhibited exceptionally low TWBCs (836 +/- 166 /microl; n = 10); this was less than half of the TWBCs of all other bat species, which ranged from 1,714 +/- 297/microl for Molossus bondae (n = 20) to 7,339 +/- 1,503/microl for Trachops cirrhosus (n = 6). Species with higher TWBCs tended to have lower Hct values. Overall, blood cell morphology was similar to other mammalian species. A large number of polychromatophilic erythrocytes and differences in lymphocyte morphology were noted. This study provides important hematological values for Neotropical bat species and significantly expands the knowledge on basal physiological measurements of Chiroptera.     

The use of an acoustic device to identify the epidural space in cattle

Twelve healthy cattle (weighing 188–835 kg) were placed in stocks and sedated with xylazine. Caudal epidural puncture was performed using an acoustic device that indicated a decrease in resistance with a change in pitch. Lidocaine was injected to verify correct needle placement by assessing needle prick stimuli applied on the left and right side of the tail root and the perineal region, and the loss of tail and anal sphincter tone. Pressure measurements were recorded during penetration of the different tissue layers and in the epidural space. A clear and sudden decrease in the pitch of the acoustic signal was audible in all 12 cattle. All cows showed clinical effects indicating successful epidural anaesthesia. The pressure in the epidural space after puncture was ?19 ± 10 mm Hg. The device may be of assistance in identifying the epidural space in cattle.     

Simulation of the seasonal cycles of bird, equine and human West Nile virus cases

The West Nile virus (WNV) is an arthropod-borne virus (arbovirus) circulating in a natural transmission cycle between mosquitoes (enzootic vectors) and birds (amplifying hosts). Additionally, mainly horses and humans (dead-end hosts) may be infected by blood-feeding mosquitoes (bridge vectors). We developed an epidemic model for the simulation of the WNV dynamics of birds, horses and humans in the U.S., which we apply to the Minneapolis metropolitan area (Minnesota). The SEIR-type model comprises a total of 19 compartments, that are 4 compartments for mosquitoes and 5 compartments or health states for each of the 3 host species. It is the first WNV model that simulates the seasonal cycle by explicitly considering the environmental temperature. The latter determines model parameters responsible for the population dynamics of the mosquitoes and the extrinsic incubation period. Once initialized, our WNV model runs for the entire period 2002-2009, exclusively forced by environmental temperature. Simulated incidences are mainly determined by host and vector population dynamics, virus transmission and herd immunity, respectively. We adjusted our WNV model to fit monthly totals of reported bird, equine and human cases in the Minneapolis metropolitan area. From this process we estimated that the proportion of actually WNV-induced dead birds reported by the Centers for Disease Control and Prevention is about 0.8%, whereas 7.3% of equine and 10.7% of human cases were reported. This is consistent with referenced expert opinions whereby about 10% of equine and human cases are symptomatic (the other 90% of asymptomatic cases are usually not reported). Despite the restricted completeness of surveillance data and field observations, all major peaks in the observed time series were caught by the simulations. Correlation coefficients between observed and simulated time series were R=0.75 for dead birds, R=0.96 for symptomatic equine cases and R=0.86 for human neuroinvasive cases, respectively.     

Explaining Usutu virus dynamics in Austria: model development and calibration

Usutu virus (USUV), a flavivirus of the Japanese encephalitis virus complex, was for the first time detected outside Africa in the region around Vienna (Austria) in 2001 by Weissenb?ck et al. [Weissenb?ck, H., Kolodziejek, J., Url, A., Lussy, H., Rebel-Bauder, B., Nowotny, N., 2002. Emergence of Usutu virus, an African mosquito-borne flavivirus of the Japanese encephalitis virus group, central Europe. Emerg. Infect. Dis. 8, 652-656]. USUV is an arthropod-borne virus (arbovirus) circulating between arthropod vectors (mainly mosquitoes of the Culex pipiens complex) and avian amplification hosts. Infections of mammalian hosts or humans, as observed for the related West Nile virus (WNV), are rare. However, USUV infection leads to a high mortality in birds, especially blackbirds (Turdus merula), and has similar dynamics with the WNV in North America, which, amongst others, caused mortality in American robins (Turdus migratorius). We hypothesized that the transmission of USUV is determined by an interaction of developing proportion of the avian hosts immune and climatic factors affecting the mosquito population. This mechanism is implemented into the present model that simulates the seasonal cycles of mosquito and bird populations as well as USUV cross-infections. Observed monthly climate data are specified for the temperature-dependent development rates of the mosquitoes as well as the temperature-dependent extrinsic-incubation period. Our model reproduced the observed number of dead birds in Austria between 2001 and 2005, including the peaks in the relevant years. The high number of USUV cases in 2003 seems to be a response to the early beginning of the extraordinary hot summer in that year. The predictions indicate that >70% of the bird population acquired immunity, but also that the percentage would drop rapidly within only a couple of years. We estimated annually averaged basic reproduction numbers between R (0)=0.54 (2004) and 1.35 (2003). Finally, extrapolation from our model suggests that only 0.2% of the blackbirds killed by USUV were detected by the Austrian USUV monitoring program [Chvala, S., Bakonyi, T., Bukovsky, C., Meister, T., Brugger, K., Rubel, F., Nowotny, N., Weissenb?ck, H., 2007. Monitoring of Usutu virus activity and spread by using dead bird surveillance in Austria, 2003-2005. Vet. Microbiol. 122, 237-245]. These results suggest that the model presented is able to quantitatively describe the process of USUV dynamics.     

Occupational swine exposure and Hepatitis E virus,Leptospira, Ascaris suum seropositivity and MRSA colonization in Austrian veterinarians, 2017–2018—A cross‐sectional study

We investigated the prevalence of Hepatitis E Virus (HEV), Leptospira and Ascaris suum (A. suum) seropositivity, and of nasal methicillin‐resistant Staphylococcus aureus (MRSA) colonization among Austrian practising veterinarians, and assessed the association with occupational swine livestock exposure. The 261 participants completed a questionnaire on demographics, intensity of occupational swine livestock contact and glove use during handling animals and their secretions. Participants' blood samples were tested for HEV, Leptospira and A. suum seropositivity and nasal swabs cultured for MRSA. We compared swine veterinarians (defined as >3 swine livestock visits/week) to non‐swine veterinarians (≤3 swine livestock visits/week) with regard to the outcomes through calculating prevalence ratio (PR) and 95% confidence interval (CI). Furthermore, the relationship between occupational swine livestock contact and the study outcomes was examined by age (</≥55 years) and glove usage. The prevalence of nasal MRSA colonization was 13.4% (95% CI: 9.3–17.6), of HEV seropositivity 20.8% (95% CI: 15.8–25.7) and A. suum seropositivity 44% (95% CI: 37.7–50.2). The highest anti‐leptospiral antibodies titres were 1:200 (L. hebdomadis) and 1:100 (L. autumnalis, L. caicola) found in three non‐swine veterinarians. Compared to non‐swine veterinarians, swine veterinarians were 1.9 (95% CI: 1.0–3.4) and 1.5 (95%CI: 1.0–2.3) times more likely HEV seropositive and A. suum seropositive, respectively, and 4.8 (95%CI: 2.5; 9.3) times more likely nasally colonized with MRSA. Among glove‐using veterinarians, occupational swine contact was no longer a determinant for HEV seropositivity (PR 1.6; 95% CI: 0.8–2.9). Similar was found for A. suum seropositivity, which was no longer associated with occupational swine livestock contact in the subgroup of glove using, ≥55‐year‐old veterinarians (PR: 1.07; 95% CI: 0.4–3.3). Our findings indicate that >3 occupational swine livestock visits per week is associated with HEV and A. suum seropositivity and nasal MRSA colonization and that glove use may play a putative preventive role in acquiring HEV and A. suum. Further analytical epidemiological studies have to prove the causality of these associations.     

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Professor Ernst Assmann zum 70. Geburtstag

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