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At least 55 records · Page 3Linked to original sources
PubMed1991

Control of rickettsial diseases.

Prevention of rickettsial infections is aimed at individual control and epidemic measures (especially in epidemic typhus), vector and rodent control, milk pasteurization (in Q fever), chemoprophylaxis and immunoprophylaxis. In vector and rodent control, the main obstacle is the rise in resistance to insecticides and rodenticides. For this reason in vector control, apart from insecticides, enhancement of the natural immunity acquired by animals in response to tick infestation and vaccination with concealed tick antigens as well as the use of hormones, chemosterilants and genetic manipulation can also be considered. For short-term high-risk exposure, doxycycline may be an effective prophylaxis of illness but may not prevent infection with scrub typhus or spotted fever group rickettsiae. At present, for specific prevention by vaccination, only Q fever vaccines are available for common use. However, development of subunit vaccines, namely immunogenic rickettsial proteins, cloned and expressed in Escherichia coli, seems to be very promising.

Animals↗
PubMed1980

Nutritional adequacy and quality control of rodent diets.

One of the most often neglected variables in experimental investigations using rodents is the diet. Recent observations that diets can influence the response of a rodent to the drug, chemical or other factors under study, with biased interpretation of results, have drawn great interest. In order to be assured that the biologic response observed is a reflection of the material or condition under study, it is imperative that the diet provide essential nutrients in the proper proportions and that contaminants be kept to a minimum. Quality control is the key to these requirements; rodent diets can provide adequate nutrition, free of significant contamination. The diets which can be provided vary according to the degree of refinements; the three major types are (1) natural product, (2) semipurified and (3) chemically defined diets. Natural product diets may be open or closed formula, depending on the amount of information that the label reveals. Guaranteed analyses of proximate nutrients are provided but are of little use in assessing the nutrient value of the formulation. The National Academy of Sciences, National Research Council publications on laboratory animal nutrient requirements should be available to all investigators using experimental animals to help them evaluate the nutritional adequacy of the diets they use. Rats and mice may be considered together under some circumstances relative to crude dietary needs, but the Syrian golden hamster should be treated separately for purposes of diet. This species appears to digest foods more like a ruminant. An ideal diet for rodents is not on the horizon because of variable needs relative to different types of research and holding. Storage and shelf life of rodent diets also play important roles in providing adequate nutrition. Variations in moisture, temperature and exposure to other chemicals can affect the quality of the feed and research results. In addition, a number of chemical and biological contaminants have been found in rodent diets, and surveillance over such variables must be a part of all laboratory animal diet quality control. Federal regulatory mandates now require that investigators assure that nutrient requirements of animals are met and that diets are reasonably free from contamination. Accepted practices in good management, formulation, shipping and storage will help achieve these commendable goals.

Animal Feed↗
PubMed1972

Biological and behavioural studies of rodents as a basis for control.

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.

Animals↗
PubMed1987

Transplantation of insulin-like growth factor-II-secreting tumors into nude rodents.

Restricted supplies of insulin-like growth factor II (IGF-II) have severely limited investigation of the in vivo actions of this hormone. To circumvent this problem, we have developed an in vivo rodent model in which rat (r) IGF-II-secreting cells (18, 54-SF) are transplanted into congenitally immunodeficient (nude) rats and mice. These cells proliferate and form discrete tumors that contain rIGF-II and abundant IGF-II receptors. The tumors also secrete rIGF-II into the circulation, resulting in plasma rIGF-II concentrations many-fold greater than those in control rodents (81 +/- 19 vs. less than 10 ng/ml, rats; 159 +/- 28 vs. 18 +/- 5 ng/ml, mice; P less than 0.05, both groups). There was no significant difference between the tumor-bearing and control rodents in either body weight or tail length. The tumor-bearing rodents did have significantly lower concentrations of IGF-I (296 +/- 23 vs. 527 +/- 67 ng/ml, rats; 300 +/- 26 vs. 482 +/- 70 ng/ml, mice; P less than 0.05, both groups), suggesting that the increased concentrations of rIGF-II may have inhibited IGF-I production or secretion. This animal model may be used to explore the biological effects of increased plasma IGF-II concentrations.

Adenoma↗
PubMed1991

An experience in the control of plague in Botswana.

In October 1989, cases of human plague started to occur in Boteti district of Botswana. One hundred and seventy cases were recorded in total from 15 October 1989 to 6 April 1990. There were 12 deaths, giving a case fatality rate of 7%. All cases were of the bubonic type. A concerted control strategy based on sentinel surveillance, involving public education, flea and rodent control, chemotherapy and chemoprophylaxis controlled the epidemic.

Adolescent↗
PubMed1993

Use of an oestrogen, androgen or gestagen as a potential chemosterilant for control of rat and mouse populations.

Three synthetic steroids were evaluated as potential chemosterilants for rodent control. Ethinyl oestradiol, methyl testosterone or Org 5933, a synthetic gestagen, were incorporated into paraffin blocks containing cereal grains and offered to laboratory rats and mice in addition to their standard laboratory diet. Ethinyl oestradiol (50 mg kg-1 paraffin block) was highly unpalatable to female rats, and the amount of steroid ingested was not sufficient to interfere with their oestrous cycles or inhibit ovulation. Methyl testosterone (5000 mg kg-1 paraffin block), although not as palatable as untreated blocks, was effective in inducing almost immediate infertility in female rats and mice at an ingested dose of about 35 micrograms g-1 body weight day-1. This infertility persisted throughout the duration of treatment, and lasted for several weeks after the cessation of treatment. Male rats became infertile after 3 months of treatment owing to suppression of spermatogenesis. Female rats developed a specific aversion to methyl testosterone when they were pregnant or lactating; it was therefore not possible to masculinize the brains of their female offspring. In mice, the androgen treatment induced high levels of aggression in the females so that they fought with males and with one another. One female died of her wounds. Org 5933 (4 mg kg-1 paraffin block) was highly palatable to female rats and mice, and at doses of about 420 ng g-1 body weight day-1 was effective in inhibiting ovulation in rats within 3 to 4 days after the start of treatment. This infertility persisted throughout the duration of treatment, and the animals conceived within 5 days of cessation of treatment. A dose of about 930 ng g-1 body weight day-1 was not completely effective in inhibiting ovulation in mice, but females that became pregnant during treatment gave birth to dead young. When the gestagen was given to female rats and mice in the last few days of pregnancy, the duration of gestation was significantly prolonged, and most young were born dead; some of the females also died in labour. The gestagen did not appear to inhibit lactogenesis, since the few animals that gave birth to live young reared them normally for the first 5 days of life. These results show that either methyl testosterone or Org 5933 in paraffin blocks could perhaps be used as a chemosterilant for the control of rat and mouse populations.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1967

Use of repellents and attractants in filariasis control.

The ways in which repellents and attractants could be used to interrupt the transmission of bancroftian filariasis, especially by Culex pipiens fatigans, are assessed. Dimethyl phthalate (DMP) is an effective repellent against C. p. fatigans. It is also very toxic to all larval stages of Wuchereria bancrofti. The median lethal time to microfilariae of a solution of about 0.2% in normal saline is about 10 minutes. Other stages are similarly sensitive. Contact with DMP in very thin films is almost immediately lethal. It is highly unlikely that infection could take place under ordinary conditions through skin treated with DMP for at least many hours afterwards. This toxicity made it impossible to evaluate repellency in vitro. An in vivo test of the effect of skin applications of DMP on microfilaria counts gave anomalous results. A schedule for filariasis control, involving education, garbage disposal, rodent control, sewage disposal, and mosquito control, is proposed, and the research needed to allow repellents and attractants to play a full role in such a schedule is delineated.

Animals↗
PubMedDate not supplied

The black death past and present. 1. Plague in the 1980s.

This paper considers firstly the epidemiology of plague in the 1980s. The largest number of cases occurred in Tanzania. Most cases were in children and young adults; in the USA the male:female ratio was about 2:1. Plague had a seasonal distribution. Almost all cases arose from bites of infected rodent fleas, and Rattus spp. were the most important reservoir hosts. Virulence is linked with the presence of a 45 MDa plasmid. The predominant clinical form of plague is bubonic, followed by septicaemic, meningitic and pneumonic. For treatment, streptomycin is the antibiotic of choice, with tetracycline and chloramphenicol as alternatives. Treatment given on the first 1-2 d of illness is highly effective, and resistance is not a problem. Rodent control, insecticide application, and avoidance of contact with rodents and their fleas remain the prime means of control. Plague vaccine is not in general use.

Animals↗
PubMed1992

Biosecurity and minimal disease herds.

The minimal disease concept is a way of raising pigs so that some specific diseases are absent. Many bacteria and viruses can be transferred by pigs, air, or mechanical contact. To avoid contamination, the herd location should take into consideration disease transmission possibilities. Herd health status and source herd health status should be continuously monitored. To maintain herd health status, specific rules need to be followed for herd construction and establishment, compound perimeter, people movement, down time, animal transportation, feed use and delivery, vehicle movement, material, dead animal disposition, and rodent control. All new incoming animals should go through quarantine, and in some herds, safer methods such as AI, embryo transfer, MEW, or hysterectomy and fostering need to be used.

Animal Feed↗
PubMed1989

Seroprevalence of murine typhus and fièvre boutonneuse in certain human populations in Egypt.

A study was conducted between 1984 and 1987 to determine the prevalence of Rickettsia typhi and Rickettsia conorii infections among humans residing in the Nile Delta, Suez Canal area and Nile Valley of Egypt. Serum specimens were obtained from garbage and rodent control workers, other unclassified occupational workers, and from patients with fever of undetermined aetiology. All sera were assayed for IgA + IgM + IgG (IgAMG) antibody mixture and if positive, reassayed for specific IgM antibody to rickettsia by the indirect fluorescent antibody technique. R. typhi antibody was found in 19% (33/178) of the garbage collectors, whereas only 1% (2/178) had demonstrable antibody to R. conorii. Among those with other occupations, R. typhi antibody was detected in 0.7% (2/295) and none had R. conorii antibody. The antibody prevalence rate for R. typhi among patients with febrile illness ranged from 25 to 41%, and from 2 to 15% for R. conorii, at three different locations in Egypt. In addition, IgM antibody to R. typhi was demonstrated in some patients showing symptoms compatible with rickettsial disease and in some patients who seroconverted, indicating that R. typhi was the cause of illness among some of these patients. These findings support previous observations that R. typhi and R. conorii are the causes of human rickettsial disease in Egypt, and that humans are commonly infected with R. typhi.

Adult↗