Biological and behavioural studies of rodents as a basis for control. (9/25)

Domestic rodents, particularly those living in urban populations, represent a serious public health problem, and effective control measures are required to deal with this threat to human health. Because of the characteristic interactions between individual animals, certain behaviour patterns occur in rodent populations that are of particular concern to control biologists. The genus Rattus is an extremely diverse group whose ecological requirements are variable and flexible, while the genus Mus, on account of its small size, limited range, and modest requirements in terms of food and water, is also very difficult to control. For any control operation a knowledge of the growth dynamics of domestic rodent populations is needed; after a period of logarithmic growth, population increases cease when the habitat is fully exploited. Consequently, control operations that merely remove some animals lead only to renewed population growth. Trapping, poisoning, and predation are traditional control measures of this kind. Environmental modification is a more certain, but more difficult, approach. The use of chemosterilants offers some hope of radical control in the future, but at present, although some field trials have been made, these substances are not available for general use, one reason being their lack of specificity. Another problem connected with the use of chemosterilants is that, on account of the sexual behaviour and physiology of domestic rodents, it would be necessary to reach nearly 100% of the population to obtain effective control.  (+info)

Chemosterilization of Culex pipiens fatigans Wiedemann by exposure of aquatic stages. 3. Induction of dominant lethal mutations in the F 1 generation by certain aziridines, phosphoramides, and s-triazines. (10/25)

In insects it is known that the chemosterilant treatment induces dominant lethal mutations which bring about embryonic death. The possibility of delayed expression of the chemosterilant-induced dominant lethals in F(1) progeny of the tropical house mosquito, Culex pipiens fatigans Wiedemann has been investigated. The chemosterilants employed were 8 aziridinyl compounds, 3 phosphoramides, and 4 s-triazines. In general, all the chemosterilants tested were found to cause different degrees of mortality at different life stages of the F(1) progeny. In this respect the aziridinyl compounds were more effective than the phosphoramides and s-triazines. This effect of the chemosterilants may be useful in the sterile-male technique.  (+info)

Dispersal and survival in the field of chemosterilized, irradiated, and cytoplasmically incompatible male Culex pipiens fatigans. (11/25)

Comparative field studies were made on the dispersal and survival of chemosterilized, irradiated, and cytoplasmically incompatible (D3 strain) male Culex pipiens fatigans. There was no significant difference in dispersal patterns and daily survival rates between laboratory colony males and wild males, and between chemosterilized or irradiated males and untreated males. Although there was no difference in dispersal between adults of the D3 strain and the laboratory colony of the Delhi strain, the former had a lower daily survival rate.  (+info)

Prospects of chemosterilant and genetic control of rodents. (12/25)

This paper discusses some requirements of an ideal rodent chemosterilant, analyses the advantages of chemosterilants over other control methods, and compares the potential values of chemosterilants that affect females, males, and both sexes. Examples are given of specific situations where chemosterilants will be valuable in rodent control, together with suggested methods of applying them. The theory and practicability of using genetics in rodent control are also discussed. Neither the chemosterilant nor the genetic method is expected to become a panacea, but their eventual application will be a significant advance in rodent-control technology. Since both approaches are based on sound biological principles and are relatively safe, they should be helpful in regulating rodent populations in the future.  (+info)

The importance of ecological studies in the control of tsetse flies. (13/25)

The author reviews recent ecological research on tsetse flies in East Africa and Northern Nigeria, particularly in connexion with the flies' sensory reactions, and stresses the importance of an accurate knowledge of their daytime and night-time resting-sites and of identifying the sources of their blood meals in order to elucidate the reservoirs of trypanosomiasis. The epidemiology of the disease is considered in the light of studies of trypanosome infections in host and fly. The control of tsetse flies must be based on the practical application of ecological knowledge by methods involving either a direct attack upon the fly (such as trapping or the use of insecticides) or an indirect attack (such as bush clearing or game destruction to eliminate the fly's habitat or food supply); these methods are dealt with in some detail. The author concludes with a discussion of modern trends in research, and a number of lines of research are suggested.  (+info)

Analysis of insect chemosterilants. (14/25)

Background information concerning the concept of insect chemosterilization and analytical methods for determining trace levels of 19 P- and/or S- containing chemicals of current interest are presented. GC retention times of the compounds on 6 different columns and their p-values in 11 solvent systems are tabulated. The utility of the flame photometric detector for determining subnanogram levels of the sterilants in biological substrates is illustrated.  (+info)

Sterilization of Culex pipiens fatigans Wiedemann by apholate. (15/25)

The use of alkylating agents has been found to be a promising way of chemosterilizing mosquitos for control purposes. The investigation discussed in the present paper has shown that apholate (2,2,4,4,6,6-hexahydro-2,2,4,4,6,6-hexakis (1-aziridinyl)-1,3,5,2,4,6-triazatriphosphorine) can induce sterility rates of from 43% to 95% in Culex pipiens fatigans Wiedemann treated in the larval stage, and from 80% to 100% in C. fatigans treated in the adult stage; treatment in the pupal stage produced no significant sterility.Of the methods of application of the apholate tested (immersion of larvae and pupae in water containing apholate, exposure of anaesthetized adults to residual deposits of apholate and dusting of anaesthetized adults with apholate powder), the dusting method was found to be effective.Apholate induces sterility in both sexes. Females were affected much more when they were treated in the adult stage. The average number of eggs laid by a treated female was found to be reduced no matter whether the treatment was during the larval or the adult phase.Male mosquitos chemosterilized by dusting were more competitive than normal males.  (+info)

Duration of sterility induced in males of the tropical house mosquito, Culex pipiens fatigans Wiedemann, by the chemosterilants apholate and tepa. (16/25)

Various alkylating and non-alkylating agents are known to induce sterility in Culex pipiens fatigans, but the duration of the sterilizing effect they produce had not so far been studied for this species. The authors therefore investigated the duration of sterility induced by the alkylating chemosterilants apholate and tepa in C. p. fatigans, second-instar larvae being exposed to 10 ppm apholate or pupae to 3570 ppm tepa. They found that, in experiments in which treated males were mated once only, both apholate and tepa induced sterility lasting at least 48 days. However, in experiments in which males were mated once weekly for 6 weeks apholate-treated males showed a slight recovery from the early sterilizing effect. On the other hand, tepa was found to be very effective in inducing lasting sterility throughout the 6 successive matings. The probable reasons for the recovery from sterility of apholate-treated males and the more lasting sterility of tepa-treated males are discussed.  (+info)