An experimental evaluation of conventional control measures against the sheep tick, Ixodes ricinus (L.) (Acari: Ixodidae). II. The dynamics of the tick-host interaction

1985 ◽  
Vol 75 (3) ◽  
pp. 501-518 ◽  
Author(s):  
Sarah E. Randolph ◽  
Gordon M. Steele
Keyword(s):  
Ixodes Ricinus ◽  
Control Method ◽  
Control Strategies ◽  
Stocking Density ◽  
Experimental Manipulation ◽  
Control Measures ◽  
Effective Control ◽  
Contact Rate ◽  
Host Interaction ◽  
Questing Ticks

AbstractThe experimental manipulation of separate, but originally identical, populations of Ixodes ricinus (L.) by applying three conventional tick control measures in different enclosures on naturally infested moorland in Wales allowed the elements of the tick-host interaction to be analysed quantitatively and the effectiveness of the control methods to be compared. From the relationship between the sheep stocking density and the numbers of questing ticks picked up by fortnightly blanket-dragging in each enclosure, the death rate of ticks during their activity season and the rate of contact between sheep and ticks were calculated. From this, it was possible to investigate the effect of different stocking densities on the feeding success of ticks. A major factor determining the much lower contact rate for larvae than for nymphs was the different spatial distribution of questing ticks, clumped for larvae and random for nymphs. The non-random use by sheep of the three different vegetation zones in the paddock resulted in the highest contact rate between sheep and ticks in the pasture area, but tick survival was apparently highest in the bog area. Combining these factors resulted in the prediction that the bracken area was the least favourable habitat for ticks. In the two enclosures where the sheep were not treated with acaricide the mean tick loads on the sheep were similar, but the lower overall use of the pasture by the sheep in the low stocking density enclosure (2/ha) resulted in slightly lower tick loads there compared with those in the high stocking density enclosure (4/ha). The numbers of ticks counted in the second year showed that pasture spelling was the most effective control method, acaricide treatment was less effective, and the benefits of halving the stocking density were marginal. The implications of these results for control strategies are discussed.

scholarly journals Control Strategies for the Third wave of COVID-19 infection in India: A Mathematical Model Incorporating Vaccine Effectiveness

2022 ◽  
Author(s):  
Ashutosh Mahajan ◽  
Namitha Sivadas ◽  
Pooja Panda
Keyword(s):  
Transmission Rate ◽  
Control Strategies ◽  
Control Measures ◽  
Disease Spread ◽  
Effective Control ◽  
Third Wave ◽  
Social Distancing ◽  
Vaccination Rates ◽  
New Variant ◽  
The Future

The waning effectiveness of the COVID-19 vaccines and the emergence of a new variant Omicron has given rise to the possibility of another outbreak of the infection in India. COVID-19 has caused more than 34 million reported cases and 475 thousand deaths in India so far, and it has affected the country at the root level, socially as well as economically. After going through different control measures, mass vaccination has been achieved to a large extent for the highly populous country, and currently under progress. India has already been hit by a massive second wave of infection in April-June, 2021 mainly due to the delta variant, and might see a third wave in the near future that needs to be controlled with effective control strategies. In this paper, we present a compartmental epidemiological model with vaccinations incorporating the dose-dependent effectiveness. We study a possible sudden outbreak of SARS-CoV2 variants in the future, and bring out the associated predictions for various vaccination rates and point out optimum control measures. Our results show that for transmission rate 30% higher than the current rate due to emergence of new variant or relaxation of social distancing conditions, daily new cases can peak to 250k in March 2022, taking the second dose effectiveness dropping to 50% in the future. A combination of vaccination and controlled lockdown or social distancing is the key to tackling the current situation and for the coming few months. Our simulation results show that social distancing measures show better control over the disease spread than the higher vaccination rates. <br>

scholarly journals Modeling the Effective Control Strategy for the Transmission Dynamics of Global Pandemic COVID-19

2020 ◽  
Author(s):  
M. H. A. Biswas ◽  
M. S. Khatun ◽  
A. K. Paul ◽  
M. R. Khatun ◽  
M. A. Islam ◽  
...  
Keyword(s):  
Maximum Principle ◽  
Control Strategies ◽  
Pontryagin’S Maximum Principle ◽  
Control Measures ◽  
Effective Control ◽  
Human Immune System ◽  
Pontryagin's Maximum Principle ◽  
Social Distancing ◽  
Novel Coronavirus ◽  
Major Factors

AbstractThe novel coronavirus disease (namely COVID-19) has taken attention because of its deadliness across the globe, causing a massive death as well as critical situation around the world. It is an infectious disease which is caused by newly discovered coronavirus. Our study demonstrates with a nonlinear model of this devastating COVID-19 which narrates transmission from human-to-human in the society. Pontryagin’s Maximum principle has also been applied in order to obtain optimal control strategies where the maintenance of social distancing is the major control. The target of this study is to find out the most fruitful control measures of averting coronavirus infection and eventually, curtailed of the COVID-19 transmission among people. The model is investigated analytically by using most familiar necessary conditions of Pontryagin’s maximum principle. Furthermore, numerical simulations have been performed to illustrate the analytical results. The analysis reveals that implementation of educational campaign, social distancing and developing human immune system are the major factors which can be able to plunge the scenario of becoming infected.

scholarly journals A model for evaluating intervention strategies to control salmonella in the poultry meat production chain

2000 ◽  
Vol 124 (3) ◽  
pp. 365-373 ◽  
Author(s):  
M. J. NAUTA ◽  
A. W. VAN DE GIESSEN ◽  
A. M. HENKEN
Keyword(s):  
Control Strategies ◽  
Intervention Strategies ◽  
Control Measures ◽  
Poultry Meat ◽  
Effective Control ◽  
Meat Production ◽  
Policy Makers ◽  
Production Chain ◽  
Transmission Parameters ◽  
Salmonella Control

A model of the transmission of salmonella through the poultry meat production chain is developed, to predict the effects of intervention strategies for salmonella control. The model first describes the situation before intervention in terms of salmonella prevalences at flock level and some transmission parameters. After single control measures are translated into effects on these transmission parameters, the effects of sets of control measures (intervention strategies), can be calculated with the model. As research data are lacking, the model input parameters were derived from expert opinion. As an example, the effects of two intervention strategies proposed for the Dutch poultry industry are predicted. A sensitivity analysis is performed to indicate where the most effective control measures may be expected. Additionally, the reliability of the model predictions is studied by an uncertainty analysis. The use of the model as a tool for policy makers deciding about salmonella control strategies is discussed.

scholarly journals Schistosoma transmission in a dynamic seasonal environment and its impact on the effectiveness of disease control

2020 ◽  
Author(s):  
Qimin Huang ◽  
David Gurarie ◽  
Martial Ndeffo-Mbah ◽  
Emily Li ◽  
Charles H King
Keyword(s):  
Seasonal Variation ◽  
Intermediate Host ◽  
Control Strategies ◽  
Control Measures ◽  
Seasonal Effects ◽  
Effective Control ◽  
Optimal Timing ◽  
Snail Population ◽  
Dynamics And Control ◽  
The Impact

Abstract Background A seasonal transmission environment including seasonal variation of snail population density and human-snail contact patterns can affect the dynamics of Schistosoma infection and the success of control interventions. In projecting control outcomes, conventional modeling approaches have often ignored seasonality by using simplified intermediate-host modeling, or by restricting seasonal effects through use of yearly averaging. Methods We used mathematical analysis and numerical simulation to estimate the impact of seasonality on disease dynamics and control outcomes, and to evaluate whether seasonal averaging or intermediate-host reduction can provide reliable predictions of control outcomes. We also examined whether seasonality could be used as leverage in creation of effective control strategies. Results We found models that used seasonal averaging could grossly overestimate infection burden and underestimate control outcomes in highly seasonal environments. We showed that proper intra-seasonal timing of control measures could make marked improvement on the long-term burden reduction for Schistosoma transmission control, and we identified the optimal timing for each intervention. Seasonal snail control, implemented alone, was less effective than mass drug administration, but could provide additive impact in reaching control and elimination targets. Conclusion Seasonal variation makes Schistosoma transmission less sustainable and easier to control than predicted by earlier modeling studies.

scholarly journals Effects of medical resource capacities and intensities of public mitigation measures on outcomes of COVID-19 outbreaks

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Xia Wang ◽  
Qian Li ◽  
Xiaodan Sun ◽  
Sha He ◽  
Fan Xia ◽  
...  
Keyword(s):  
Prevention And Control ◽  
Control Strategies ◽  
Control Measures ◽  
Mitigation Measures ◽  
Effective Control ◽  
Medical Resource ◽  
Key Factors ◽  
Medical Resources ◽  
Detection Rates ◽  
And Control

Abstract Background The COVID-19 pandemic is complex and is developing in different ways according to the country involved. Methods To identify the key parameters or processes that have the greatest effects on the pandemic and reveal the different progressions of epidemics in different countries, we quantified enhanced control measures and the dynamics of the production and provision of medical resources. We then nested these within a COVID-19 epidemic transmission model, which is parameterized by multi-source data. We obtained rate functions related to the intensity of mitigation measures, the effective reproduction numbers and the timings and durations of runs on medical resources, given differing control measures implemented in various countries. Results Increased detection rates may induce runs on medical resources and prolong their durations, depending on resource availability. Nevertheless, improving the detection rate can effectively and rapidly reduce the mortality rate, even after runs on medical resources. Combinations of multiple prevention and control strategies and timely improvement of abilities to supplement medical resources are key to effective control of the COVID-19 epidemic. A 50% reduction in comprehensive control measures would have led to the cumulative numbers of confirmed cases and deaths exceeding 590,000 and 60,000, respectively, by 27 March 2020 in mainland China. Conclusions Multiple data sources and cross validation of a COVID-19 epidemic model, coupled with a medical resource logistic model, revealed the key factors that affect epidemic progressions and their outbreak patterns in different countries. These key factors are the type of emergency medical response to avoid runs on medical resources, especially improved detection rates, the ability to promote public health measures, and the synergistic effects of combinations of multiple prevention and control strategies. The proposed model can assist health authorities to predict when they will be most in need of hospital beds and equipment such as ventilators, personal protection equipment, drugs, and staff.

scholarly journals Predicting spread and effective control measures for African swine fever– should we blame the boars?

2019 ◽  
Author(s):  
Rachel A. Taylor ◽  
Tomasz Podgórski ◽  
Robin R. L. Simons ◽  
Sophie Ip ◽  
Paul Gale ◽  
...  
Keyword(s):  
At Risk ◽  
Wild Boar ◽  
Control Strategies ◽  
Control Measure ◽  
African Swine Fever ◽  
Control Measures ◽  
Effective Control ◽  
Risk Of Infection ◽  
Long Distance ◽  
Baltic Countries

SummaryAfrican swine fever (ASF) has been causing multiple outbreaks in Russia, Poland and the Baltic countries in recent years and is currently spreading westwards throughout Europe and eastwards into China, with cases occurring in wild boar and domestic pigs. Curtailing further spread of ASF requires full understanding of the transmission pathways of the disease. Wild boars have been implicated as a potential reservoir for the disease and one of the main modes of transmission within Europe. We developed a spatially explicit model to estimate the risk of infection with ASF in boar and pigs due to the natural movement of wild boar that is applicable across the whole of Europe. We demonstrate the model by using it to predict the probability that early cases of ASF in Poland were caused by wild boar dispersion. The risk of infection in 2015 is computed due to wild boar cases in Poland in 2014, compared against the reported cases in 2015 and then the procedure is repeated for 2015-2016. We find that long- and medium-distance spread of ASF (i.e. >30km) is very unlikely to have occurred due to boar dispersal, due in part to the generally short distances boar will travel (<20km on average). We also predict what the relative success of different control strategies would have been in 2015, if they were implemented in 2014. Results suggest that hunting of boar reduces the number of new cases, but a larger region is at risk of ASF compared to no control measure. Alternatively, introducing boar-proof fencing reduces the size of the region at risk in 2015, but not the total number of cases. Overall, our model suggests wild boar movement is only responsible for local transmission of disease, thus other pathways are more dominant in medium and long distance spread of the disease.

scholarly journals Analysis of Control Interventions against Malaria in communities with Limited Resources

2021 ◽  
Vol 29 (2) ◽  
pp. 71-91
Author(s):  
E.A. Bakare ◽  
B.O. Onasanya ◽  
S. Hoskova-Mayerova ◽  
O. Olubosede
Keyword(s):  
Optimal Control ◽  
Malaria Transmission ◽  
Control Strategies ◽  
Indoor Residual Spraying ◽  
Control Measures ◽  
Limited Resources ◽  
Effective Control ◽  
Bed Nets ◽  
Multiple Control ◽  
Potential Impact

Abstract The aim of this paper is to analyse the potential impact of multiple current interventions in communities with limited resources in order to obtain optimal control strategies and provide a basis for future predictions of the most effective control measures against the spread of malaria. We developed a population-based model of malaria transmission dynamics to investigate the effectiveness of five different interventions. The model captured both the human and the mosquito compartments. The control interventions considered were: educational campaigns to mobilise people for diagnostic test and treatment and to sleep under bed nets; treatment through mass drug administration; indoor residual spraying(IRS) with insecticide to reduce malaria transmission; insecticide treated net (ITN) to reduce morbidity; and regular destruction of mosquito breeding sites to reduce the number of new mosquito and bites/contact at dusks and dawn. Analysis of the potential impact of the multiple control interventions were carried out and the optimal control strategies that minimized the number of infected human and mosquito and the cost of applying the various control interventions were determined.

scholarly journals Control Strategies for the Third wave of COVID-19 infection in India: A Mathematical Model Incorporating Vaccine Effectiveness

2021 ◽  
Author(s):  
Namitha A Sivadas ◽  
Ashutosh Mahajan ◽  
Pooja Panda
Keyword(s):  
Transmission Rate ◽  
Control Strategies ◽  
Control Measures ◽  
Disease Spread ◽  
Effective Control ◽  
Third Wave ◽  
Social Distancing ◽  
Vaccination Rates ◽  
New Variant ◽  
The Future

The waning effectiveness of the COVID-19 vaccines and the emergence of a new variant Omicron has given rise to the possibility of another outbreak of the infection in India. COVID-19 has caused more than 34 million reported cases and 475 thousand deaths in India so far, and it has affected the country at the root level, socially as well as economically. After going through different control measures, mass vaccination has been achieved to a large extent for the highly populous country, and currently under progress. India has already been hit by a massive second wave of infection in April-June, 2021 mainly due to the delta variant, and might see a third wave in the near future that needs to be controlled with effective control strategies. In this paper, we present a compartmental epidemiological model with vaccinations incorporating the dose-dependent effectiveness. We study a possible sudden outbreak of SARS-CoV2 variants in the future, and bring out the associated predictions for various vaccination rates and point out optimum control measures. Our results show that for transmission rate 30% higher than the current rate due to emergence of new variant or relaxation of social distancing conditions, daily new cases can peak to 250k in March 2022, taking the second dose effectiveness dropping to 50% in the future. Combination of vaccination and controlled lockdown or social distancing is the key to tackling the current situation and for the coming few months. Our simulation results show that social distancing measures show better control over the disease spread than the higher vaccination rates.

scholarly journals Wildlife and damage to agriculture: an ethnobiological approach with rural producers in southeastern Brazil

2019 ◽  
Vol 27 (1) ◽  
pp. 17-26
Author(s):  
Ana Laura Campos de Carvalho ◽  
Adrielli Ribeiro Araújo ◽  
Théa Mirian Medeiros Machado ◽  
Rômulo Ribon ◽  
Leonardo Esteves Lopes
Keyword(s):  
Control Method ◽  
Control Strategies ◽  
Human Dimensions ◽  
Wild Animal ◽  
Effective Control ◽  
Southeastern Brazil ◽  
Economic Losses ◽  
Pest Species ◽  
Structured Interviews ◽  
Rural Producers

AbstractSome wild animal species quickly adapt to anthropogenic environments, producing unusually large populations, causing human-wildlife conflicts. The objective of this study is to understand the way the farmers perceive the fauna and the information they possess regarding the damages those animais inflict on their crops in southeastern Brazil. We collected data by presenting 200 questionnaires and conducting 22 semi-structured interviews with the rural producers in a region characterized by an agrarian matrix intermixed with small forest patches. Nearly every rural producer (99%) who answered the questionnaire (n = 107) had suffered wild animal-triggered economic losses, especially by the White-eyed Parakeet Psittacara leucophthalmus (51%), which attacked maize and fruit crops. A substantial portion of these farmers (38%) has employed some control method, including acoustic techniques (42.5%), like fireworks, and visual techniques (41%), like scarecrows. The farmers concurred that effective control methods are necessary for the White-eyed Parakeet, as current techniques proved inadequate. The understanding that the rural producers possess about the problem will facilitate designing new control strategies to manage this pest species. However, to ensure its success, a suitable management plan must be formulated to guarantee that the local rural occupations are maintained, incorporating human dimensions into wildlife management.

scholarly journals Zoonotic Tuberculosis in Humans: Control, Surveillance, and the One Health Approach

2019 ◽  
Vol 41 (1) ◽  
pp. 130-144
Author(s):  
Rodrigo Macedo Couto ◽  
Otavio T Ranzani ◽  
Eliseu Alves Waldman
Keyword(s):  
Low Income ◽  
One Health ◽  
Control Strategies ◽  
Diagnostic Methods ◽  
Surveillance Data ◽  
Control Measures ◽  
Low Income Countries ◽  
Effective Control ◽  
Surveillance Systems ◽  
And Control

Abstract Zoonotic tuberculosis is a reemerging infectious disease in high-income countries and a neglected one in low- and middle-income countries. Despite major advances in its control as a result of milk pasteurization, its global burden is unknown, especially due the lack of surveillance data. Additionally, very little is known about control strategies. The purpose of this review was to contextualize the current knowledge about the epidemiology of zoonotic tuberculosis and to describe the available evidence regarding surveillance and control strategies in high-, middle-, and low-income countries. We conducted this review enriched by a One Health perspective, encompassing its inherent multifaceted characteristics. We found that the burden of zoonotic tuberculosis is likely to be underreported worldwide, with higher incidence in low-income countries, where the surveillance systems are even more fragile. Together with the lack of specific political commitment, surveillance data is affected by lack of a case definition and limitations of diagnostic methods. Control measures were dependent on risk factors and varied greatly between countries. This review supports the claim that a One Health approach is the most valuable concept to build capable surveillance systems, resulting in effective control measures. The disease characteristics and suggestions to implement surveillance and control programs are discussed.

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