Bite Rate Research Articles

Hydrodynamic mediation of killifish predation on infaunal polychaetes

AbstractTo explore predator‐prey interactions between California killifish (Fundulus parvipinnis) and spionid polychaetes (Polydora cornuta and Streblospio benedicti) in saltmarsh creeks, we conducted a laboratory flume experiment to quantify whether killifish prey‐patch selectivity varies with water flow. The flume included a 300‐cm2 area of defaunated sediment within which we centrally positioned 24 P. cornuta, 24 S. benedicti, or no worms as a control. We videotaped groups of three killifish for 50 min at one of six unidirectional flow speeds (3 cm s−1, 6 cm s−1, 9 cm s−1, 12 cm s−1, 15 cm s−1, or 18 cm s−1) and recorded their bite rate anywhere in the sediment vs. bites directed at the central patch containing worms (98 cm2). The number of bites anywhere in the 300‐cm2 sediment area increased as flow increased from 3 cm s−1 to 6 cm s−1 and declined linearly as flow increased further. The number of bites anywhere was lower in treatments with no worms than when either worm species was present. The percentage of bites directed at the central patch varied significantly with flow speed and worm presence. With defaunated sediment only, ∼ 33% of bites were directed at the central patch at all flows, consistent with a null model of nonselective foraging. When either worm species inhabited the central patch, ∼ 65% of bites were directed at the central patch at 3 cm s−1 and 6 cm s−1, with patch selection declining as flow increased. Despite differences in morphology and behavior, the two prey species elicited similar foraging activity by killifish. These results suggest the importance of hydrodynamics in driving these epibenthic predator‐prey interactions.

Algal nitrogen and phosphorus content drive inter- and intraspecific differences in herbivore grazing on a Caribbean reef

Identifying how herbivorous reef fish select resources is an important aspect of understanding how coral reef communities are structured. Ecological stoichiometry, built around the mass balance of elements, necessitates that to build tissue, maintain growth, and reproduce, animals must maintain a homeostatic balance of elements within their body. Nitrogen (N) and phosphorus (P) are abundant in animal tissue relative to most plants and algae. Accordingly, N and P are often limiting for herbivores, which should therefore focus their foraging efforts on resources rich in these elements. Here, we explore how variation in N and P concentrations in algae impact herbivore resource selectivity on a coral reef. We conducted feeding assays using a brown alga from the genus Sargassum grown under elevated nitrogen (N), phosphorus (P) or both (N+P). Overall bite rates were higher on N enriched, but not P enriched, assays but individual foraging efforts varied among species and fish size. Individual Sparisoma aurofrenatum increased the number of bites taken per feeding foray on N enriched algae while Acanthurus coeruleus and Sparisoma rubripinne fed more on P enriched assays. Sparisoma chrysopterum increased their foraging effort on both N and P enriched assays. However, the influence of algal nutrient content on foraging effort declined with increasing fish size, such that full grown fishes did not respond to assay nutrient content. Overall, preference for enriched algae resulted in ~20% more consumption of N and N+P enriched algae relative to unenriched controls. Our study is the first to link the elemental nutrient content of algae to species-specific feeding decisions of reef herbivores and demonstrates the utility of ecological stoichiometry to explore herbivory on coral reefs.

Effect of supplementation frequency in feeding behavior, displacement patterns and forage intake of beef heifers

Our work was carried out to evaluate forage intake, feeding behavior and displacement patterns of beef heifers fed exclusively on pasture or receiving oat grain, either daily (“frequent”) or from Monday to Friday (“infrequent”), in two phenological stages of Alexandergrass (Urochloa plantaginea Link.): “Vegetative” and “Reproductive”. The grazing method was continuous, with a variable number of animals. The experimental design was completely randomized with measures repeated in time with three feeding frequencies and two phenological stages. Forage intake was estimated using the chromic oxide technique as an indicator of fecal output. Heifers on exclusive Alexandergrass pasture and frequently supplemented had higher forage intake of dry matter (DM, 2.91 kg DM 100 kg BW-1) than those that were infrequently supplemented (2.00 kg DM 100 kg BW-1). Forage intake was greater in the “Vegetative” stage. The use of feeding stations is modified in response to supplementation frequency and phenological stages of Alexandergrass. Bite mass was higher for daily supplemented heifers, and these animals spent less time grazing. Also, bite mass was the item that best explained DM total ingestion. Bite mass and grazing time were similar throughout the phenological stages, whereas bite rate decreased in the reproductive stage. Feeding behavior and forage intake responses of beef heifers were influenced by supplementation frequency and phenological stages of Alexandergrass.

Correlation between production performance and feeding behavior of steers on pasture during the rainy-dry transition period.

The aim of this study was to evaluate the correlation between production performance and feeding behavior of steers reared on pasture during the rainy-dry transition period. Twenty-two ½ Holstein-Zebu crossbred steers at an average age of 10months and with an average initial body weight of 234.5±16.0kg were distributed in a completely randomized design with two types of supplementation and eleven replications. Pearson's linear correlation analysis was performed between behavioral variables and weight gain and feed conversion. Correlation coefficients were tested by the t test. The time expended feeding at the trough was positively correlated (P<0.05) with average daily gain (ADG) and with the number of periods of permanence at the trough. Bite rate and the number of bites per day were positively correlated (P<0.05) with ADG and negatively (P<0.05) with feed conversion, unlike the number of bites per swallow, which was negatively correlated (P<0.05) with ADG. There was a positive correlation (P<0.05) between feed efficiency in dry matter and neutral detergent fiber and ADG. Feeding behavior characteristics have little association with the production performance of cattle on pasture receiving mineral or energy-protein supplementation.

Bubble Curtains: Herbivore Exclusion Devices for Ecology and Restoration of Marine Ecosystems?

Herbivorous fishes play a critical role in maintaining or disrupting the ecological resilience of many kelp forests, coral reefs and seagrass ecosystems, worldwide. The increasing rate and scale of benthic habitat loss under global change has magnified the importance of herbivores and highlights the need to study marine herbivory at ecologically relevant scales. Currently, underwater herbivore exclusions (or inclusions) have been restricted to small scale experimental plots, in large part due to the challenges of designing structures that can withstand the physical forces of waves and currents, without drastically altering the physical environment inside the exclusion area. We tested the ability of bubble curtains to deter herbivorous fishes from feeding on seaweeds as an alternative to the use of rigid exclusion cages. Kelps (Ecklonia radiata) were transplanted onto reefs with high browsing herbivore pressure into either unprotected plots, exclusion cages or plots protected by bubble curtains of 0.785 m2 and 3.14 m2. Remote underwater video was used to compare the behavioural response of fishes to kelps protected and unprotected by bubble curtains. Kelp biomass loss was significantly lower inside the bubble curtains compared to unprotected kelps and did not differ from kelp loss rates in traditional exclusion cages. Consistent with this finding, no herbivorous fishes were observed entering into the bubble curtain at any point during the experiment. In contrast, fish bite rates on unprotected kelps were 1621 ± 702 bites hr-1 (mean ± SE). Our study provides initial evidence that bubble curtains can exclude herbivorous fishes, paving the way for future studies to examine their application at larger spatial and temporal scales, beyond what has been previously feasible using traditional exclusion cages.

Alteration of plant species assemblages can decrease the transmission potential of malaria mosquitoes.

Knowledge of the link between a vector population's pathogen-transmission potential and its biotic environment can generate more realistic forecasts of disease risk due to environmental change. It also can promote more effective vector control by both conventional and novel means.This study assessed the effect of particular plant species assemblages differing in nectar production on components of the vectorial capacity of the mosquito Anopheles gambiae s.s., an important vector of African malaria.We followed cohorts of mosquitoes for three weeks in greenhouse mesocosms holding nectar-poor and nectar-rich plant species by tracking daily mortalities and estimating daily biting rates and fecundities. At death, a mosquito's insemination status and wing length were determined. These life history traits allowed incorporation of larval dynamics into a vectorial capacity estimate. This new study provided both novel assemblages of putative host plants and a human blood host within a nocturnal period of maximum biting.Survivorship was significantly greater in nectar-rich environments than nectar-poor ones, resulting in greater total fecundity. Daily biting rate and fecundity per female between treatments was not detected. These results translated to greater estimated vectorial capacities in the nectar-rich environment in all four replicates of the experiment (means: 1,089.5 ± 125.2 vs. 518.3 ± 60.6). When mosquito density was made a function of survival and fecundity, rather than held constant, the difference between plant treatments was more pronounced, but so was the variance, so differences were not statistically significant. In the nectar-poor environment, females' survival suffered severely when a blood host was not provided. A sugar-accessibility experiment confirmed that Parthenium hysterophorus is a nectar-poor plant for these mosquitoes.Synthesis and applications. This study, assessing the effect of particular plant species assemblages on the vectorial capacity of malaria mosquitoes, highlights the likelihood that changes in plant communities (e.g. due to introduction of exotic or nectar-rich species) can increase malaria transmission and that a reduction of favourable nectar sources can reduce it. Also, plant communities' data can be used to identify potential high risk areas. Further studies are warranted to explore how and when management of plant species assemblages should be considered as an option in an integrated vector management strategy.

Browsing and plant traits in nutrient-rich and nutrient-poor savannas in Tanzania

Abstract:Environmental productivity is important in determining defensive or tolerance traits of plants, with nutrient-rich savannas showing tolerance and nutrient-poor showing defence traits. Animals are affected differently by such traits due to differences in size, and other characters. We studied differences in browsing as a response to plant traits by elephant, giraffe and impala in Mikumi, a nutrient-poor savanna, and Serengeti, a nutrient-rich savanna, both in Tanzania, for a total of 4 mo; 2 mo at each site. Browsing time on a plant, species and height browsed were recorded. Spinesence reduced biting rate by elephant in Serengeti to 3.8 bites min−1, compared with 4.7 without spines, but had no effect on impala or giraffe. Leaf size affected biting rate by giraffe, decreasing with size in Serengeti from 19.8 bites min−1 to 17.4 bites min−1, increasing in Mikumi, from 17.7 to 19.5 bites min−1, but did not differ in elephant and impala. Biting rate by elephant in Serengeti decreased with browsing height from 0.6 m to 4.2 m and by impala in Mikumi decreased from 0.25 m to 1.5 m, while that of giraffe in Mikumi increased with browsing height, peaking at 4.2 m. The effect was comparable for elephant and impala.

A reduction in malaria transmission intensity in Northern Ghana after 7\xa0years of indoor residual spraying

BackgroundIndoor residual spraying (IRS) is being implemented as one of the malaria prevention methods in the Northern Region of Ghana. Changes in longevity, sporozoite and entomological inoculation rates (EIRs) of major malaria vectors were monitored to assess the impact of IRS in selected districts.MethodsMonthly human landing catches (HLCs) were used to collect mosquitoes from sentinel sites in three adjacent districts between July 2009 and December 2014: Savelugu Nanton (SND) where IRS had been implemented from 2008 to 2014; Tolon Kumbungu (TKD) where IRS had been implemented between 2008 and 2012 and Tamale Metropolis (TML) with no history of IRS. Mosquitoes were morphologically identified to species level and into sibling species, using PCR. Samples of Anopheles gambiae sensu lato (s.l.) were examined for parity and infectivity. EIR was calculated from biting and infectivity rates of malaria vectors.ResultsParity rates of An. gambiae s.l. decreased significantly (p < 0.0001) in SND from 44.8% in 2011 to 28.1% by 2014, and in TKD from 53.3% in 2011 to 46.6% in 2012 (p = 0.001). However 2 years after IRS was discontinued in TKD, the proportion of parous An. gambiae s.l. increased significantly to 68.5% in 2014 (p < 0.0001). Parity rates in the unsprayed district remained high throughout the study period, ranging between 68.6% in 2011 and 72.3% in 2014. The sum of monthly EIRs post-IRS season (July–December) in SND ranged between 2.1 and 6.3 infective bites/person/season (ib/p/s) during the 3 years that the district was sprayed with alphacypermethrin. EIR in SND was reduced to undetectable levels when the insecticide was switched to pirimiphos methyl CS in 2013 and 2014. Two years after IRS was withdrawn from TKD the sum of monthly EIRs (July–December) increased by about fourfold from 41.8 ib/p/s in 2012 to 154.4 ib/p/s in 2014. The EIR in the control area, TML, ranged between 35 ib/p/s in 2009 to 104.71 ib/p/s by 2014.ConclusionsThis study demonstrates that IRS application did have a significant impact on entomological indicators of malaria transmission in the IRS project districts of Northern Ghana. Transmission indicators increased following the withdrawal of IRS from Tolon Kumbungu District.

Erratum to: Modelling the effects of malaria infection on mosquito biting behaviour and attractiveness of humans

We develop and analyse a deterministic population-based ordinary differential equation of malaria transmission to consider the impact of three common assumptions of malaria models: (1) malaria infection does not change the attractiveness of humans to mosquitoes; (2) exposed mosquitoes (infected with malaria but not yet infectious to humans) have the same biting rate as susceptible mosquitoes; and (3) mosquitoes infectious to humans have the same biting rate as susceptible mosquitoes. We calculate the basic reproductive number, \(R_0\), for this model and show the existence of a transcritical bifurcation at \(R_0=1\), in common with most epidemiological models. We further show that for some sets of parameter values, this bifurcation can be backward (subcritical). We show with numerical simulations that increasing the relative attractiveness of infectious humans, increases \(R_0\) but reduces the equilibrium prevalence of infectious humans; decreasing the biting rate of exposed mosquitoes increases \(R_0\) and the equilibrium prevalence of infectious humans and mosquitoes; and increasing the biting rate of infectious mosquitoes has no impact on \(R_0\) or the equilibrium prevalence of infectious humans, but decreases the infectious prevalence of infectious mosquitoes. These analyses of a simple malaria model show that common assumptions around the relative attractiveness of infectious humans and the relative biting rates of exposed and infectious mosquitoes can have substantial and counter-intuitive effects on malaria transmission dynamics.

Production performance and milk fatty acid profile in grazing dairy cows offered ground corn or liquid molasses as the sole supplemental nonstructural carbohydrate source

The objective of this study was to compare the effects of ground corn or liquid molasses fed as the sole supplemental nonstructural carbohydrate (NSC) source on production performance, milk fatty acid (FA) profile, grazing behavior, and N metabolism in grazing dairy cows. A strip-grazing management system was used, with cows offered a new strip of fresh herbage after each milking, resulting in approximately 16 h of access to pasture daily. Animals were fed a diet formulated to yield an 86:14 forage-to-concentrate ratio consisting [dry matter (DM) basis] of 74% mixed grass-legume herbage, 12% mixed-mostly legume baleage, 12% NSC source, and 2% mineral-vitamin premix. Twenty Jersey cows averaging (mean ± standard deviation) 121 ± 73 d in milk in the beginning of the study were randomly assigned to 1 of 2 herbage supplementation treatments: (1) baleage plus ground corn (B+GC) or (2) baleage + liquid molasses (B+LM). Both NSC sources were fed at a flat rate of 1.6 kg of DM/cow daily. The study lasted from June to September for a total of 15 wk with data and sample collection conducted in wk 3, 7, 12, and 15. Milk samples for FA analysis were collected in wk 2, 4, 6, 8, 9, 11, and 13. Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) for a randomized complete block design with repeated measures over time. Treatment × week interactions were observed for supplement DM intake, milk urea N, bite rate, urinary excretion of uric acid, and milk FA (e.g., 17:0, 18:0, cis-9,trans-11 18:2). Supplement DM intake was greatest in cows fed B+LM in wk 7, 12, and 15. Compared with cows fed B+GC, those fed B+LM had lower concentrations of milk urea N in wk 7 and 15. Milk yield, concentrations and yields of milk components, and plasma concentrations of essential AA, except Met, which was lowest with feeding B+LM, were not affected by supplementation. The plasma concentration of urea N was lowest with feeding B+LM. Cows fed B+GC spent more time grazing than those fed B+LM. Feeding B+GC increased cis-9 18:1 FA and most trans-18:1 FA in milk, whereas B+LM increased Σ odd-chain FA, Σ n-3 FA, and the trans-11 18:1 to trans-10 18:1 ratio, and decreased the n-6 to n-3 ratio. Based on current results, B+LM can entirely replace B+GC without negatively affecting milk yield or yields and concentrations of milk fat and true protein, while decreasing milk urea N, plasma urea N, and the milk trans-11 18:1 to trans-10 18:1 ratio, and increasing Σ n-3 FA.

Modeling the Impact of Bed-Net Use and Treatment on Malaria Transmission Dynamics.

We modeled the impact of bed-net use and insecticide treated nets (ITNs), temperature, and treatment on malaria transmission dynamics using ordinary differential equations. To achieve this we formulated a simple model of mosquito biting rate that depends on temperature and usage of insecticides treated bed nets. We conducted global uncertainty and sensitivity analysis using Latin Hypercube Sampling (LHC) and Partial Rank Correlation Coefficient (PRCC) in order to find the most effective parameters that affect malaria transmission dynamics. We established the existence of the region where the model is epidemiologically feasible. We conducted the stability analysis of the disease-free equilibrium by the threshold parameter. We found the condition for the existence of the endemic equilibrium and provided necessary condition for its stability. Our results show that the peak of mosquitoes biting rate occurs at a range of temperature values not on a single value as previously reported in literature. The results also show that the combination of treatment and ITNs usage is the most effective intervention strategy towards control and eradication of malaria transmissions. Sensitivity analysis results indicate that the biting rate and the mosquitoes death rates are the most important parameters in the dynamics of malaria transmission.

A method using optimized combinations based on energy spectrum extension factor to reduce MAI in asynchronous DS-CDMA systems

The principle to suppress multiple access interference (MAI) using double chip waveforms (DCW) in asynchronous DS-CDMA systems is analyzed in the paper. Based on the principle, a new method adopting optimized combinations of chip waveforms (CCW) to reduce MAI is proposed. The energy spectrum extension factor (ESEF) of equivalent chip waveform is introduced to optimally select CCW to reduce MAI, improve the signal to interference plus noise ratio (SINR) and bite error rate (BER) performance of asynchronous DS-CDMA users. The general closed form expression of SINR for asynchronous DS-CDMA users with CCW is obtained. The BER is also derived by improved Gaussian approximation (IGA). The theoretical analysis and numerical simulation results show that the optimized CCW using ESEF can effectively suppress MAI better, achieve higher SINR and BER performance compared with DCW. Moreover, the overlap between the simulation and IGA BER curves verifies the theoretical derivation.

Resource partitioning by two syntopic sister species of butterflyfish (Chaetodontidae)

Resource partitioning is considered one of the main processes driving diversification in ecological communities because it allows coexistence among closely related and ecologically equivalent species. We combined three complementary approaches, i.e. the evaluation of foraging behaviour, diet composition and nutritional condition (RNA:DNA ratio), to assess feeding by two closely related (sister) butterflyfishes that are syntopic in Puerto Rico. Chaetodon capistratus had a higher abundance and higher bite rate and selected octocorals and hard corals for feeding, whereas Chaetodon striatus fed preferentially on sandy substrates. Cnidarians and polychaetes were the most representative diet items for both species, but C. capistratus preferred the former (Feeding Index of 74.3%) and C. striatus the latter (Feeding Index of 60.4%). Similar RNA:DNA ratios for both species suggest that, although they differ in feeding rates and diet, C. capistratus and C. striatus have similar nutritional fitness. Therefore, these species are both zoobenthivores but show clear differences in their substrate selection. The differences in the use of foraging substrate by C. capistratus and C. striatus, despite their close phylogenetic relationship and similar diets, suggest that these species coexist by resource partitioning.

Changes in the short‐term intake rate of herbage by heifers grazing annual grasses throughout the growing season

AbstractAnnual temperate grasses go through abrupt changes in morphological composition during the growing season, which can affect ingestive behavior of grazing cattle. However, few studies have examined the effects of gradual structural changes in annual temperate pastures on the herbage intake rate during the growing season. We hypothesized that lenient grazing (removal of 40% of the initial pre‐grazing height) maintains short‐term intake rate (STIR) of grazing cattle over the entire growing season, even with decreased leaf/stem ratios. The studied pastures contained Avena strigosa, Lolium multiflorum and a mixture of the two species. Short‐term intake rate was measured using the double weighing technique, evaluating both bite rate and bite mass. The percentage of stem + pseudostem and leaf lamina lengths in the herbage mass were measured. Relationships between sward structure and animal ingestive behavior were also examined. As the pasture growing season progressed, the STIR of heifers grazing annual temperate grass swards was affected more by the time required to take a bite than by bite mass. Moreover, the sward structure also changed after each grazing cycle, reducing the pre‐grazing leaf/stem ratio. However, reductions in the pre‐grazing leaf lamina mass (up to 37% of the sward herbage mass) and/or in the leaf lamina length (up to 52% of the extended tiller height) did not affect the STIR of grazing heifers, since the animals maintained their bite mass and time per bite. In summary, with a grazing down target of 40% of the pre‐grazing height, reductions in STIR of heifers grazing annual temperate grasses occurred when the pre‐grazing leaf lamina percentage was &lt;37% of the sward herbage mass and/or &lt;52% of the extended tiller height. These results suggested that to avoid STIR reductions during the last grazing cycles, managements to stimulate tillering and delay stem + pseudostem elongation are necessary and should be investigated.

The esperanza window trap reduces the human biting rate of Simulium ochraceum s.l. in formerly onchocerciasis endemic foci in Southern Mexico.

BackgroundThe Esperanza Window Trap (EWT) baited with CO2 and human sweat compounds is attractive to Simulium ochraceum s.l., the primary vector of Onchocerca volvulus in the historically largest endemic foci in México and Guatemala.Methodology/Principal findingsThe ability of the EWT to locally reduce numbers of questing S. ochraceum s.l. was evaluated in two formerly onchocerciasis endemic communities in Southern México. At each community, two EWTs were placed in or near a school or household and flies were collected sequentially for a total of 10 days. Black fly collections were then carried out for an additional 10 days in the absence of the EWTs. Flies were also collected outside the dwellings to control for variations in the local fly populations. When the EWTs were present, there was a significant reduction in the human biting rate at both the household and school locations at collection sites, with a greater effect observed in the schools.Conclusions/SignificanceThese results indicate that the EWTs not only have potential as a black fly monitoring tool but may be used for reducing personal exposure to fly bites in Mesoamerica.

Mathematical model of Zika virus with vertical transmission.

Zika is a flavivirus transmitted to humans through either the bites of infected Aedes mosquitoes or sexual transmission. Zika has been linked to congenital anomalies such as microcephaly. In this paper, we analyze a new system of ordinary differential equations which incorporates human vertical transmission of Zika virus, the birth of babies with microcephaly and asymptomatically infected individuals. The Zika model is locally and globally asymptotically stable when the basic reproduction number is less than unity. Our model shows that asymptomatic individuals amplify the disease burden in the community, and the most important parameters for ZIKV spread are the death rate of mosquitoes, the mosquito biting rate, the mosquito recruitment rate, and the transmission per contact to mosquitoes and to adult humans. Scenario exploration indicates that personal-protection is a more effective control strategy than mosquito-reduction strategy. It also shows that delaying conception reduces the number of microcephaly cases, although this does little to prevent Zika transmission in the broader community. However, by coupling aggressive vector control and personal protection use, it is possible to reduce both microcephaly and Zika transmission. 2000 Mathematics Subject Classifications: 92B05, 93A30, 93C15.

The architectural design of trees protects them against large herbivores

Summary Where large browsers are abundant, the survival of trees depends on their ability to deploy defences, either chemical or structural. Structural defences include the arrangement of dense and intricate architecture, termed ‘cage’ architecture. Previous studies showed that trees developing in herbivore‐rich environments tend to have more cage architecture but its precise effect on mammalian herbivores remains unknown. In this paper, we experimentally test how cage architecture affects the bite rate of goats, a generalist mammalian herbivore. We selected 11 palatable tree species with contrasting architectures. We described their caginess using an index combining spinescence and woodiness of their stems. Finally, we evaluated how the caginess of trees slows down herbivores when feeding on the inner leaves in tree crowns. We observed that the bite rate of goats on inner leaves of the cagiest trees was so severely reduced that they could not satisfy their daily nutritional requirements. We discuss how this could affect the preference of wild herbivores for less cagy trees, especially at the end of the dry season. A lay summary is available for this article.

Modeling Chagas disease in Chile: From vector to congenital transmission

Chagaś disease is a human health problem in Latin America. It is highly prevalent in northern Chile between the Arica-Parinacota and Coquimbo regions, with reported incidence of 3–11/100000 inhabitants and mortality of 0.3–0.4/100000. The interruption of vector transmission was reported in 1999 by means of the elimination of the primary vector, Triatoma infestans, from human dwellings, thus the epidemiologic dynamics of this disease should be modified. Here we model the dynamics of Chagaś disease based on previous models for vector and congenital transmission, propose a model that includes both transmission forms and perform simulations. We derive useful relationships for the reproductive number (R0) showing that it may be expressed as the sum of the vector (R0V) and congenital (R0C) contributions. The vector contribution is larger than the congenital one; without the former Chagaś disease vanishes exponentially in two to three generations. Sensitivity analyses showed that the main parameters that intervene are the human bite rate, the density of vectors per human and the mortality rate of the insect vectors. Our model showed that the success of the eradication of Chagaś disease is based on the interruption of domestic transmission. Once this is obtained, the control strategies should focus on avoiding the domiciliation of wild vectors, re-colonization by the primary vector, and an adequate coverage of congenital case treatment.

Pediatric Dog Bite Prevention: Are We Barking Up the Wrong Tree or Just Not Barking Loud Enough?

The objectives of this study were (1) to evaluate dog bite-related injuries and associated medical documentation and (2) to compare these results with a study of dog bites from the same institution 10 years prior. Data were retrospectively collected from a pediatric emergency department from July 2007 to July 2011 for patients treated for dog bites. These data were then compared with data from the same institution from 10 years prior. A total of 1017 bite injuries were treated (average, 254.25 bites/year), which represents a 25% increase compared with 10 years prior. Comparing the 1997 and 2007 to 2011 cohorts, patient demographics, bite rate among children less than 5 years old, rate of dog breed documentation, and setting of injury were similar. Dog breed was reported in 47% (95% confidence interval [CI], 40.2-53.9) and 41% (95% CI, 38.0-44.0) of cases, respectively, in the 2 cohorts. Bites to the craniofacial region were most common (face only reported for 1997: 43.2%; 95% CI, 36.4-50 versus 2007-2011: 66.1%; 95% CI, 63.2-69.0). In both cohorts, the child's home was the most frequent setting, accounting for 43% of bites (1997: 95% CI, 30.2-55.9 and 2007-2011: 95% CI, 39.3-46.7). Pediatric dog bites continue to occur frequently, and the associated factors did not change over the 10-year period: young age of child, bites to the craniofacial region, and dogs familiar to the child. Although accurate medical documentation of dog bites is a prerequisite to develop effective prevention strategies, current medical documentation of dog bites may be misguided.

Mathematical modeling for explanation and prediction of treatment outcome in growing patients with anterior open bite malocclusion treated with rapid molar intruder and posterior bite blocks

PurposeRapid molar intruder (RMI) is a non-compliant treatment modality for correction of anterior open bite (AOB) in growing patients. The aim of this study is to explain the main treatment outcome (increase in overbite) by the other morphological changes after treatment with RMI and posterior bite blocks (PBBs). We also investigated the baseline characteristics that may help predict the treatment outcome. Subjects and methodsFourteen patients (mean age±SD=10.7±1.7year) with AOB malocclusion were treated with RMI springs and PBBs fixed on posterior teeth for 4 months. Patients were assessed before and after treatment using cephalometric radiographs. Multivariable regression model was developed to explain overbite change by the other morphological components. Single regressions of overbite change on baseline variables were conducted to determine best predictor of treatment outcome. ResultsTreatment produced significant increase in overbite. The change in overbite was best explained by the changes in facial axis angle, upper anterior dental heights and upper posterior dental heights. The best predictor for treatment outcome was the facial axis angle before treatment. ConclusionThe correction of AOB by the RMI may be explained by orthopedic and dental changes resulting from growth and treatment. The orthopedic changes consisting of counterclockwise mandibular true rotation is the strongest contributor to overbite increase. Patients with severe vertical growth pattern tend to have greater closure rate of open bite.