Prevalence of Mycobacterium avium in slaughter pigs in The Netherlands and comparison of IS1245 restriction fragment length polymorphism patterns of porcine and human isolates

A significant increase in the incidence of caseous lesions in the lymph nodes of slaughter pigs prompted a large-scale investigation in five slaughterhouses in The Netherlands. In total, 158,763 pigs from 2,899 groups underwent gross examination. At least one pig with caseous lesions in the submaxillary and/or mesenteric lymph nodes was observed in each of 154 of the 2,899 groups examined (5%). In total, 856 pigs (0.5%) were affected. As many as five pigs in each of 141 of the 154 positive groups (91.5%) had lymph node lesions. Greater numbers of pigs with affected lymph nodes were found in 13 groups (8.5%). Four pigs had lesions in the kidneys, liver, or spleen. Acid-fast bacteria were detected by microscopic examination of 121 of 292 Ziehl-Neelsen-stained smears of caseous lesions (41%). In a follow-up study, Mycobacterium avium complex (MAC) bacteria were isolated from 219 of 402 affected lymph nodes (54.2%). Ninety-one of the isolated strains were analyzed by restriction fragment length polymorphism (RFLP) typing with insertion sequence IS1245 as a probe. All but 1 of these 91 strains contained IS1245 DNA, indicating that pigs in The Netherlands carried almost exclusively M. avium bacteria and no other bacteria of MAC. Only one pig isolate exhibited the bird-type RFLP pattern. MAC isolates from 191 human patients in The Netherlands in 1996 were also typed by RFLP analysis. Computer-assisted analysis showed that the RFLP patterns of 61% of the human isolates and 59% of the porcine isolates were at least 75% similar to the RFLP patterns of the other group of strains. This indicates that pigs may be an important vehicle for M. avium infections in humans or that pigs and humans share common sources of infection.

Potency of veterinary rabies vaccines in The Netherlands: a case for continued vigilance

Commercial rabies vaccines, used by veterinarians in the Netherlands, were collected for testing in the mouse potency test. Of the six vaccines tested, two were clearly below the minimal requirements for potency of 1.0 IU. Of these six vaccines the rabies virus glycoprotein (GP) and nucleoprotein (NP) contents were determined in an antigen competition ELISA. The GP content proved to correlate well with the potency found in the mouse potency test (r = 0.95, p < 0.01), whereas no such correlation was found for the NP content (r approximately 0, p > 0.05). After the manufacturers were told about the results, one of the two vaccines that did not comply with the requirements was withdrawn from the market. Measurement of the GP content of a second lot of the remaining vaccines indicated that sufficiently high levels of GP were present in all five. Additional in vivo testing in mice for efficacy against intracerebral challenge with the Dutch bat rabies virus EBL1-12 resulted in acceptable levels of protection with four of these five vaccines of the second lot. The data presented illustrate the need for continued potency evaluation of veterinary rabies vaccines in the Netherlands.

Hantavirus infections in The Netherlands: epidemiology and disease

A serological survey for the prevalence of hantavirus infections in The Netherlands was carried out on > 10,000 sera, from selected human populations, and different feral and domestic animal species. Hantavirus-specific antibodies were found in about 1% of patients suspected of acute leptospirosis, 10% of patients with acute nephropathia, and in less than 0.1% haemodialysis and renal transplant patients. Among individuals with a suspected occupational risk, 6% of animal trappers, 4% of forestry workers, 2% of laboratory workers and 0.4% of farmers were seropositive. The majority of the seropositive individuals lived in rural and forested areas. The main animal reservoir of the infection was shown to be the red bank vole (Clethrionomys glareolus). Epidemiological, clinical and laboratory findings seen in serologically confirmed human cases were similar to those associated with nephropathia epidemica.

Lead intoxication in cattle: a case report

During the autumn of 1989 a feed contamination induced a widespread lead intoxication of cattle in the northern provinces of The Netherlands (Groningen and Friesland). Over 300 farms were involved, affecting about 15,500 animals (mostly dairy cattle). For a period of one to four weeks these animals took up a thousand kg of lead. This resulted in lead levels in milk, livers, and kidneys above the regulatory safety limits. Due to the chelating therapy, which was rapidly applied by the local veterinarians, only about 30 animals died of an acute lead intoxication. A joint action of the governmental and private authorities prevented exposure of consumers to lead-contaminated animal products. Based on observations, measurements and literature data, predictions were made of the lead levels to be expected in animal products and the time needed for depletion of these levels. The appropriate animals were ear-tagged to ensure their identification, and the decline in time of the lead levels in milk and offals was conscientiously monitored. In the second week of 1990 the lead concentrations were decreased to levels well below the regulatory limits, and hence the tags were removed. The present paper reports our observations and conclusions, especially regarding treatment, predictions and outcome of this incident.

[Tuberculosis in alpacas; a zoonosis as an imported disease]

In the Netherlands, in 1988, a micro-epidemic of tuberculosis in alpacas recently imported from Peru prompted health authorities to initiate investigation of human and animal contacts. Although the animal trainer and his assistant suffered from pulmonary tuberculosis, they turned out to be infected by Mycobacterium tuberculosis, while the animals later proved to be infected by M. bovis. The alpacas' caretaker and a laboratory technician present at the autopsy, were probably infected by animal contact. Elsewhere in the country, three more alpacas were reported with tuberculosis at the time; this initiated a large-scale investigation among alpacas, llamas etc., but no further cases were detected. The possibility of imported zoonoses, especially after 1992, is discussed.

[Tuberculosis in imported alpacas--a zoonosis--now what?]

An outbreak of tuberculosis caused by M. bovis in imported Alpaca's in the Netherlands is reported. A review of the outbreak of the disease is followed by a more detailed discussion of the symptoms, diagnostic testing with the tuberculin skin test and the ELISA test, the gross lesions, the bacteriological examinations, the control measures and the legal aspects. As tuberculosis is not referred to in the Live-Stock Act, the control measures had to be based on the humane Control of Infectious Disease and Tracing the Causes of Disease Act. In the discussion, it is advocated to pay attention to more species of animals than only to the traditional live-stock in the proposed Health and Welfare of Animals Act.

[Lead poisoning in cattle in north Netherlands. October 1989-January 1990]

By the end of 1989 a serious lead intoxication of cattle occurred in the northern part of the Netherlands (provinces Groningen and Friesland). This intoxication appeared to be caused by contaminated feed. Over 300 farms were stricken, with about 15,500 animals (mostly dairy cattle). In a period of one to four weeks these animals consumed about 1,000 kg of lead. This resulted in lead levels in milk, livers, and kidneys above the regulatory safety limits. Thanks to the chelating therapy that was rapidly applied by the local veterinarians, only about 30 animals died of an acute lead intoxication. The cooperating governmental and private authorities took action to prevent exposure of consumers to lead-contaminated animal products. Based on careful estimations, predictions were made of the lead levels to be expected in animals products and the time needed for depletion of these levels. The appropriate animals were marked to ensure their identification, and the decline in time of the lead levels in milk and offals was conscientiously monitored. In the second week of 1990 the lead concentrations were decreased to levels well below the regulatory limits, and hence the marks were removed from the animals.

Relaxation time constant of isolated rabbit left ventricle

Experiments were performed on isolated rabbit left ventricles. Controlled ejections during otherwise isovolumic contractions were studied. The time constant of relaxation was defined as the slope of the linear approximation of the ln(P)-t relation over a 40-ms period starting 20 ms after the minimum of the first time derivative of left ventricular pressure (dP/dt) of the isovolumic contraction. Variations in time of ejection, its amplitude, and velocity are applied independently. No direct effect of the variations in time and velocity of the ejection on the time constant of relaxation was found. This is in conflict with the findings of Hori et al. (Circ. Res. 55: 31-38, 1984). The difference is due to the influence of the recovery of pressure directly after the end of ejection in their study. This effect is present especially when ejection was timed to take place late in the contraction phase. The effect of the variation of the amplitude of the ejection on the time constant was similar to the effect of the end-diastolic pressure on the end-diastolic volume. It is concluded that the time constant of relaxation depends linearly on the same processes that are responsible for the height of the end-diastolic pressure.

The effect of controlled changes in volume on the active state of the rabbit isolated left ventricle

The contractile properties of isovolumically contracting isolated rabbit left ventricles are studied under the influence of controlled rapid volume changes during systole and diastole. The time integral of the pressure curve (TTI), representing the active state, is used to quantify the energy consumption of the ventricle. Steady state conditions resulting from an introduced volume change show a TTI/EDV relation which represents the Starling curve. However, immediately after a quick volume increase (decrease) introduced in diastole, the TTI/EDV ratio has a higher (lower) value than indicated by the Starling relation. This shows a volume dependent activation (deactivation), related to changes in the inotropic state of the heart muscle cells within the ventricular wall. A volume increase at a later moment (in systole) always produces a lower rate of activation. Indeed, if the rapid volume change is introduced at moments later than 70% of time to peak pressure, TTI is less than observed from the Starling mechanism, indicating a deactivation. When comparing the decreasing effect on the active state introduced by volume decrease during systole, it is shown that this effect is not only a function of the amplitude of the decrease itself but is highly dependent upon the way EDV is reached.

Post-extra systolic potentiation: influence of calcium and verapamil in rat and rabbit hearts

The interactions of the inotropic effects of verapamil (0.05-2.0 mumol l-1), calcium (0.33-5.2 mmol l-1) and post extra systolic potentiation (PESP) as induced by paired stimulation were studied in isolated rabbit and rat hearts under isovolumic and isotonic conditions. At low doses of verapamil, contractions were depressed, but those elicited by paired stimulation showed less depression than contractions of the same rate during single stimulation and even exceeded the unpotentiated contractions without verapamil. At high doses of verapamil contractility could not be restored by paired stimulation. Although contractions were restored to control level by an increase in extra-cellular calcium they were still abnormal in the sense that PESP could not be elicited. The excitation-contraction (e-c) uncoupling due to low calcium perfusion could be counteracted by paired stimulation but e-c uncoupling due to high dose verapamil could not be reversed by paired stimulation. Our results support the view that PESP does not only depend on augmented slow channel calcium influx but also on an enhanced calcium shift within the sarcoplasmic reticulum. We are doubtful about the idea that PESP can be used clinically to counteract the negative inotropic effect of high doses of verapamil.