Apesar de Alouatta guariba clamitans apresentar ampla distribuição na Mata Atlântica, do rio Doce (ES) ao rio Camaquã (RS) e a oeste até o norte da Argentina. The social group of the brown howler monkey, Alouatta guariba clamitans Cabrera, is typically small (2–12 individuals), with one or two adult males, and. Adult females are covered in dark brown or reddish brown hair. A latitudinal color gradient occurs in the subspecies Alouatta guariba clamitans. Males tend to be.
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In South America, yellow fever YF is an established infectious disease that has been identified outside of its traditional endemic areas, affecting human and nonhuman primate NHP populations. In the epidemics that occurred in Argentina betweenseveral outbreaks affecting humans and howler monkeys Alouatta spp were reported, highlighting the importance of this disease in the context of conservation medicine and public health policies.
Considering the lack of information about YF dynamics in New World NHP, our main goal was to apply modelling tools to better understand YF transmission dynamics among endangered brown howler monkey Alouatta guariba clamitans populations in northeastern Argentina. Two complementary modelling tools were used to evaluate brown howler population dynamics in the presence of the disease: Vortex, a stochastic demographic simulation model, and Outbreak, a stochastic disease epidemiology simulation.
ADW: Alouatta guariba: INFORMATION
The baseline model guxriba YF disease epidemiology predicted a very high probability of population decline over the clanitans years. We believe flamitans modelling approach discussed here is a reasonable description of the disease and its effects on the howler monkey population and can be useful to support evidence-based decision-making to guide actions at a regional level.
Culicidae and nonhuman primates NHPin what has been termed “sylvatic cycle” Vasconcelos et al. From those foci, epidemic waves of clamirans dissemination tend to occur in cycles of between seven years Vasconcelos et al. The periodicity of viral dissemination has been suggested to be linked with NHP population dynamics. These animals show acute forms of the disease, with severe clinical evolution and high mortality CrockettSallis et al. During the periods andthe circulation of YFV in South America was identified in areas considered for decades to be free of the disease, being detected in southeastern and southern Brazil in Vasconcelos et al.
In Misiones province clamiatns northeastern Argentina, YF was diagnosed in howler monkeys and humans Goenaga et al. Two howler alouqtta species occur in Argentina: The brown howler is the rarest primate species in Argentina, restricted to east-central Misiones province Holzmann et al. Due to the likely significant impact of these epidemics, there is special concern about the current status of this specie. In Argentina, the brown howler has been re-classified from clamitanns to “critically endangered” Agostini et al.
A group of nine experts in different fields primate ecology, eco-epidemiology, mosquito ecology and virology dedicated themselves to gathering, systematising and discussing all available data and information on brown howlers and YF in the Atlantic Forest.
Our goal in this paper is to present, in a more detailed fashion, the combined use of different modelling tools to simulate YFV transmission dynamics among brown howler monkey populations in northeastern Argentina in order to gain a better understanding of YF dynamics in New World NHP. We also describe the process of definition of the input parameters, highlighting the contribution of each one buariba the whole system.
Vortex is a Monte Carlo simulation for population viability analysis that examines the effects of deterministic forces as well as demographic, environmental and genetic stochastic events on wild population abundance and growth dynamics.
Demographic information such as breeding and mortality rates for general sex-specific stages juveniles, sub-adults and adults is user-specified and used to project total population size. Using this approach, individuals are classified as SEIR.
To model infectious processes, the state of each individual in the population is tracked and the probabilities of transition among states are specified as functions of the number of individuals in each state and of other relevant parameters, such as the contact rate and the latent period of infection.
To make the software able to model the transmission of a vector-borne disease, we conducted basic adaptations in some specific components see Input parameters for stochastic disease epidemiology models.
General approach for model construction – We decided to use the advantages of both Vortex and Outbreak to create a more realistic model representing the dynamics of YF in brown howler populations in Argentina.
A metamodel is composed of two or more independent, discipline-specific models that exchange data in order to reveal emergent dynamic properties of a complex system.
In this approach, the output of one model can modify inputs to another model e. This metamodel approach, utilising the complementary strengths of each modelling tool, allows us to analyse the population-level impacts of simulated YF outbreaks in a more detailed and realistic fashion compared to methods using each software alone. To implement metamodelling we followed Lacy et al. In our metamodel, population viability was predicted using the Vortex, while the disease epidemiological dynamics were simulated using Outbreak.
In order to evaluate the robustness of the model to parametric uncertainty, a sensitivity analysis was conducted. In general, the sensitivity of a given model input parameter measures the proportional change in a given output parameter e. In the current context, this analysis was used to uncover particularly sensitive parameters that could significantly alter the results and conclusions derived from the model.
In all models the sensitivity analysis was conducted using alternative values for variables related to demographic parameters of the howler monkeys e. Input parameters for Vortex demographic model – A general baseline population model for brown howler monkeys was built and it was later tailored to represent the populations of Misiones.
The baseline population model was designed to investigate the viability of a nonexistent but biologically accurate howler population without any anthropogenic threats. The baseline model reflects the biological potential of brown howlers. Alternative values for demographic parameters were then explored through sensitivity testing.
Scenario settings – Duration of simulation – Life expectancy of howlers is approximately years in the wild. The population was modelled for years approximately 15 generations so that long-term population trends could be observed.
One hundred years is vlamitans enough into the future so as to decrease the chances of omitting a yet unknown event, but also not too short to fail to observe a slowly developing event. Number of iterations – One thousand independent iterations were run for each scenario. Species description – Definition of extinction – Extinction was defined in the model as no animals of one or both sexes remain.
Concordance of environmental variation EV between reproductive rates and survival rates – EV is the annual variation in reproduction and survival due to variation in environmental conditions.
Making EV concordant between reproduction and aloustta means that good years for reproduction are also good years for survival and vice versa. In Vortex the EV is modelled by the user which specifies a mean and a standard deviation SD values for each rate. Environmental factors such as unpredictable rainfall, fluctuating temperatures and limiting resources to feed young are all likely to have a significant effect on juvenile mortality in general Ralls et al.
The median value estimated from analysis of studbook data for 40 captive mammal populations was 3. Reproductive clamians and rates – Breeding system [long term polygyny Mitani et al. The program uses the mean age of first reproduction rather than the earliest recorded age of reproduction. To be conservative the age of first reproduction for females was set at five years in the baseline clamotans and four years was set in the sensitivity analysis.
It was estimated that it would take longer for males to mate clamktans reproduce since they must be able to secure a troop of females cclamitans. There is a lot of discussion in the literature regarding this parameter Pope From observations in A. Maximum age – Vortex assumes that animals can reproduce at the normal rate throughout their adult life. Longevity was set as the maximum age of reproduction. Female breeding success – According to Strier et al. Claamitans, it was considered that adult females produce one infant every two years.
Different studies report different annual birth rates; the highest is recorded by Miranda with aloatta. Maximum number of offspring per clamitanw – Mortality rates – According to Gkariba et al.
Other studies seem to confirm this data e. Between ages three-four they become sub-adults and mortality rates tend to drop Agostini et al. However, males aged four years old tend to disperse more than females Oklander et al. Mortality rates of adult howler monkeys are very low Miranda However, it was estimated that for both males and females the mortality rate would increase after the age of This is because after 10 years of age, the likelihood of the male having been expelled from his group increases Pope and, if so, his mortality rate increases significantly.
For each mortality rate, alternative values based on SD were set to simulate alluatta possible impact caused by the EV Table I. Thus, more vulnerable ages, like the earlier and advanced stages of life, had higher values of SD estimated when compared with less vulnerable ages.
Population description – Number of populations – For the purpose of the baseline model one population was considered, but in reality, is composed of several smaller fragmented populations with unknown connectivity among them see Metapopulation simulation.
Initial population size n – According to a best guess the population of Misiones could be around individuals Holzmann et al. Carrying capacity K cla,itans Because we did not find a quantitative estimation of K specific for Alouatta sp. This is an assumption, similar to that made by Mandujano and Escobedo-Morales No EV was added to the K, as variations in clamjtans size are accounted for by EV in reproduction and survival.
Natural catastrophes can be tornadoes, floods, droughts, disease or similar events. These events are modelled in Vortex by assigning an annual probability of occurrence and a pair of severity factors describing their impact on survival across all age-sex classes and the proportion of females successfully breeding in a given year.
These factors range from 0 maximum or absolute effect to 1 no effect and guaribaa imposed during the single year of the catastrophe, after which time the demographic rates can rebound to their baseline values.
In this sense, a simulation was conducted using the Vortex model alone, to compare the outcome of baseline model in scenarios with and without YF outbreaks. For this specific analysis, YF was set as a potential catastrophe Crockett and an inter-epidemic interval of 15 years on average for Argentina Aloouatta Bitetti et al.
However, for the metamodel simulation, no catastrophes were set in Vortex and different probabilities of YF occurrence were defined by the sensitivity analysis using Outbreak see Contact with and transmission of virus through an external environmental source. Supplementation – No supplementation of individuals from other unrelated populations, wild or captive, was incorporated into the baseline model. A sensitivity analysis specific for the severity clamitane frequency of YF outbreaks was performed in Vortex.
Metapopulation alouattta – Due to forest fragmentation the remnant brown howler monkey population is becoming increasingly structured into subpopulations and so, might not be impacted by YF outbreaks in the same way. Thus, we tried to simulate how the population of brown howler monkey might potentially be distributed in Misiones Fig.
Dental disorders in brown howler monkeys (Alouatta guariba clamitans) maintained in captivity.
There are no specific references to support these population numbers and were based on the field experience of researchers Agostini et al. But, we believe, this simulation would be useful to illustrate the possible mechanisms related to metapopulation dynamics, not evaluated in the baseline model.
Dispersal between populations was estimated and modelled. We estimated that males dispersed more than females Oklander et al. Dispersal rates varied between fragments based on the perceived degree of connectivity and no mortality was considered.
Of the dispersing individuals, assumptions were made based on Oklander et al. Dispersal rates between populations are represented in Fig. For more details about methods for metapopulation input parameters in Vortex see Lacy et al. Input parameters for stochastic disease epidemiology models – Outbreak simulates SEIR-style disease dynamics, which means that this model calls for an encounter rate between individuals as the mechanism for direct transmission.
To guarba the model able to support the transmission of a vector-borne disease, we translated some basic components like exposed and infectious into different ways of viewing the system: First, as a simplified case, we considered only the incubation and infectivity period for the vertebrate host. In the second system, we selected the time needed to complete the full virus cycle, i.
Southern brown howler – Wikipedia
For more details about the conceptual basis for adapting directly transmitted disease to mosquito-borne disease systems see Adams and Kapan and Clamitahs et al.
Pre-susceptible state – We assume that all newly-born individuals become susceptible to YF immediately after birth, except in cases when a mother has recovered from infection with the pathogen.
This temporary immunity lasts between one days lactation period for each newborn animal, with a uniform probability of reverting to the susceptible state during this period of time Johansson et al.