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Modelling the Transmission of Rabies
Published in E. J. Clegg, J. P. Garlick, Disease and Urbanization, 1980
I mentioned earlier that a crucial question is whether, and under what circumstances, the disease would spread through the fox population if it were introduced. Suppose that one infected fox is introduced into a community of normal foxes. If it manages to transmit the disease to several other foxes before it dies, then the disease will have made a good start. If the initial fox dies before transmitting the disease, then that is the end of the matter. It turns out that the crucial question is how many new infections on the average are caused by direct transmission from one rabid fox. This quantity is called the (net) reproduction rate. If it is one or less the disease is bound to die out, although of course it may cause a small epidemic before doing so. If the reproduction rate exceeds one, there is a chance of the disease dying out, but there is now a real chance of it growing more or less indefinitely. Incidentally, only about half the rabid foxes have the ‘furious’ type of rabies, and the others are likely to be ineffective, so the furious foxes will need to have a reproduction rate greater than about two to ensure transmission. Now the reproduction rate depends on the biting habits of a rabid fox, on its period of infectivity before death, and on the density of susceptible foxes. Assuming the first two of these to be largely beyond our control, the possibility of reducing the reproduction rate seems to depend on that of reducing the density of susceptible foxes. Hence the policies of killing or immunizing a high proportion of the population. Unfortunately, it is quite difficult to estimate the reproduction rate that would obtain in any area, for little is known of the biting habits of rabid foxes. This is perhaps the biological feature which one would most like to measure in order to predict the chance that a threatened epidemic would take hold.
Lethality and effects on biological and population growth parameters of ladybird predator Hippodamia variegata (Goeze) treated by some plant essential oils
Published in Toxin Reviews, 2023
Saeed Shaltoki, Hooshang Rafiee Dastjerdi, Ali Golizadeh, Mahdi Hassanpour, Asgar Ebadollahi, Vahid Mahdavi
The result of each experiment was tested for the curve fit using PROC GENMOD procedures (PROC GLM; SPSS 2012, Robertson et al. 2007), and the data were analyzed using PROC PROBIT (PROC GLM; SPSS 2012) to determine lethal concentrations (LC50 and LC90 values) on standard and log scales with associated 95% fiducial limits. Besides, the mortality, developmental time, female and male longevity, and fecundity data were analyzed by one-way ANOVA. If significant differences were detected, the means were separated at α = 5% by the Tukey test. Daily fertility and mortality data were integrated into the form of a life table according to Carey (1993), and they were used to calculate population parameters: net reproductive rate (R0), mean generation time (T), intrinsic rate of increase (rm), doubling time (DT), and finite rate of increase (λ). Jackknife pseudo values calculated for life table parameters on different treatments were analyzed by one-way ANOVA (PROC GLM; SPSS 2012) (De Holanda Nunes Maia et al. 2014).
Impact of temperature and prey type on biology and life-table parameters of Cheyletus malaccensis Oudemans (Acari: Cheyletidae)
Published in Egyptian Journal of Basic and Applied Sciences, 2022
Ashraf S. Elhalawany, Hosnia A. Afifi, Eman L. Ayad
Life-table parameters as defined by Birch [21] were calculated using a BASIC computer program [22]. Sex ratio from each experiment was determined by visual observation and life tables were constructed from the data obtained for developmental time of immature stages and adult characteristics. Whereas: The net reproductive rate is the mean number of female offspring produced per female (R0) = Σ (lx × mx), where ‘mx’ is female progeny per female; ‘lx’ is the rate of females survival; the mean length of generation period, expressed in days (T) = Σ (x × lx × mx)/Σ(lx × mx); intrinsic rate of natural increase is a natural logarithm of the intrinsic rate of increase and indicates the number of times of population multiplication in a time unit (rm) = ln (R0)/T; means time of population to double (DT) = ln (2)/ rm and the finite rate of increase is the multiplication per female in unit time of a population with a stable age distribution (λ) = exp (rm).
Effects of three conventional insecticides on life table parameters and detoxifying enzymes activity of Pulvinaria aurantii Cockerell (Hemiptera: Coccidae)
Published in Toxin Reviews, 2021
Mohammad Fazel Hallaji Sani, Bahram Naseri, Hooshang Rafiee-Dastjerdi, Sirus Aghajanzadeh, Mohammad Ghadamyari
The life table parameters including intrinsic rate of increase (rm), net reproductive rate (R0), finite rate of increase (λ), mean generation time (T) and doubling time (DT) were calculated (Birch 1948, Southwood and Henderson 2000). Life table parameters were calculated according to the following formulae: