Historical survey data suggest that the seroprevalence of antibodies against Coxiella burnetii in the general population of The Netherlands decreased from more than 40% in 1983 to 2·4% in 2007, just before the start of the large 2007–2010 Q fever epidemic. To assess whether the sharp decline in seroprevalence was real, we performed a cross-sectional study using historical samples. We tested samples using a contemporary commercial indirect immunofluorescence assay. In plasma samples from the south of The Netherlands from 1987, we found an age- and sex-standardized seroprevalence of 14·4% (95% confidence interval 11·2–18·3). This was significantly lower than a 1983 estimate from the same area (62·5%), but significantly higher than 2008 (1·0%) and 2010 (2·3%) estimates from the same area. The study suggests that there was a steady and sharp decline in Q fever seroprevalence in the south of The Netherlands from 1987 to 2008. We assume that seroprevalence has decreased in other parts of The Netherlands as well and seroprevalence surveys in other European countries have shown a similar declining trend. Waning population immunity in The Netherlands may have contributed to the scale of the 2007–2010 Q fever epidemic. For a better understanding of the infection dynamics of Q fever, we advocate an international comparative study of the seroprevalence of C. burnetii.

Q fever patients are often reported to experience a long-term impaired health status, including fatigue, which can persist for many years. During the large Q fever epidemic in The Netherlands, many patients with a laboratory-confirmed Coxiella burnetii infection were not notified as acute Q fever because they did not fulfil the clinical criteria of the acute Q fever case definition (fever, pneumonia and/or hepatitis). Our study assessed and compared the long-term health status of notified and non-notified Q fever patients at 4 years after onset of illness, using the Nijmegen Clinical Screening Instrument (NCSI). The study included 448 notified and 193 non-notified Q fever patients. The most severely affected subdomain in both patient groups was ‘Fatigue’ (50·5% of the notified and 54·6% of the non-notified patients had severe fatigue). Long-term health status did not differ significantly between the notified and non-notified patient groups, and patients scored worse on all subdomains compared to a healthy reference group. Our findings suggest that the magnitude of the 2007–2009 Q fever outbreak in The Netherlands was underestimated when only notified patients according to the European Union case definition are considered.

Patients with a lower respiratory tract infection (LRTI) might be at risk for long-term impaired health status. We assessed whether LRTI patients without Q fever are equally at risk for developing long-term symptoms compared to LRTI patients with Q fever. The study was a cross-sectional cohort design. Long-term health status information of 50 Q fever-positive and 32 Q fever-negative LRTI patients was obtained. Health status was measured by the Nijmegen Clinical Screening Instrument. The most severely affected subdomains of the Q fever-positive group were ‘general quality of life’ (40%) and ‘fatigue’ (40%). The most severely affected subdomains of the Q fever-negative group were ‘fatigue’ (64%) and ‘subjective pulmonary symptoms’ (35%). Health status did not differ significantly between Q fever-positive LRTI patients and Q fever-negative LRTI patients for all subdomains, except for ‘subjective pulmonary symptoms’ (P = 0·048).

Investigations into some possible attractants of Glossina morsitans Westw. and G. pallidipes Aust. have been described. In small cages (8x8x11 in.) under laboratory conditions, flies with painted eyes survived longer than those that were untreated, whilst removing the antennae decreased longevity. Olfactory stimuli were probably more important than vision in orientating a fly towards a static guinea-pig used as a host in a moulded mesh insert into the cage. Field observations indicated that tsetse flies were orientated towards an ox at a distance mainly by vision and few flies found oxen concealed by screens. Olfaction may be used at relatively short distances to find hidden host animals, and G. pallidipes may respond to smell more readily than G. morsitans.

Tests in the laboratory and small field cages (6 ft3) indicated that tsetse were not attracted to any particular colour (red, yellow, blue) or shade (white, grey, black). However, in the field more flies were caught off a dark ox than a white ox. In the laboratory > 80% of male G. pallidipes responded to black light within four hours while with G. morsitans a similar proportion was attracted only after six hours. Responses by both species decreased with blue, red and white light and were least with yellow. In small field cages attraction to black light was reduced and only 20–38·6% of either species were caught by a “flap trap” in 6–13½-h test periods. Tests with either blue or red lights in these field cages trapped less than 9% of the released tsetse flies in similar periods. Field trials with black light indicated that this attractant was ineffective as a sampling technique since very few of a natural population were trapped.

Investigations into the survival and breeding of the tsetse fly Glossina morsitans Westw. in large and small cage volumes under insectary and ambient climatic conditions in the Zambezi valley, and using oxen as host animals, are described. Under ambient conditions, flies emerging from puparia collected at Kariba, and held in the insectary, survived longer than flies emerging from puparia collected at Chirundu. Flies caught from the bush did not live as long as flies emerging from puparia held in the insectary, and generally lived longer under variable than under constant climatic conditions. The survival of ‘ wild ’ flies decreased during the hot, dry months under ambient conditions. Flies lived longer and were more reproductive in small cages than in large cages. Reproduction in small cages was higher when the flies were exposed to a variable climate instead of controlled conditions, but two colonies of ‘ wild ’ flies declined under both climatic conditions. Eeproduction was better in the small, standard cages (8 × 8 × 11 in.) than in Petana boxes, while Geigy 25’s were intermediate in this respect, but survival and mean puparial weights tended to be similar. The results show a complete failure to breed G. morsitans in large cages.

Laboratory and field investigations into sex attraction and mating behaviour of Glossina morsitans orientalis Vanderplank have been described. Male flies were not attracted to volatile and soluble compounds from two- to three-day-old mature virgin females, or to virgin females in a simple olfactometer. Removal of antennae from either sex did not appreciably reduce insemination rates after 24–48-h mating periods compared with normal flies. Similar numbers of wild male flies were caught off oxen baited or non-baited with mature virgin females. G. m. orientalis probably does not produce a pheromone.

Male flies appeared to be sexually activated only after movement by the female. Mating success was reduced in the dark and when the male's eyes were painted, but blinding the female fly did not reduce insemination. Mating was similar with or without wings and halteres and the sounds produced by them.

Time between pairing the sexes and the start of mating tended to increase, and the percentage of inseminated females accepting two or more matings decreased, after the first copulation. Female flies rarely re-mated within a day. Virgin female flies accepted males passively with partly open wings, and mated females rejected further copulation with closed wings, activity to shake the male off, and primarily a downward-curved abdomen. Virgin female flies mated for periods of 1–45 min did not receive sperm but successful ad libitum mating was reduced a day later. Insemination rates decreased with females older than seven days and reached zero 28–83 days after eclosion, while 37-day-old males inseminated 93% of young females.

The ultrastructure of the merozoite of Eimeria tenella has been studied by means of electron microscopy. The first-generation merozoite is approximately 3·4 μm in length, and 1·2 μm in width, while the second-generation merozoite is approximately 10·5 μm in length and 1·5 μm in width.

The cell wall of the merozoite consists of a double membrane, but at the anterior extremity the existence of a fluted collar gives the appearance of two narrow double membranes separated by a zone of less electron-dense material. Twenty-four surface fibrils are distributed around the periphery; they extend along the entire length of the organism and lie beneath the double limiting membrane.

The anterior end of the merozoite is distinguished by a conoid apparatus which includes several components. A bulbiform outer annulus is invested by a fluted collar, and itself encloses an extrusible papilla. Two osmiophilic fibrils, the paired organelles, arise within the extrusible papilla and extend longitudinally into the cytoplasm. Twenty-four smaller fibrils, or toxonemes, also arise within the conoid and pass back into the main body of the organism.

The cytoplasm of the merozoite includes mitochondria, glycogen, dense elliptical granules and endoplasmic reticulum, together with a definite Golgi complex. A nucleus is located in the posterior third of the organism and is enclosed by a perforated double membrane. At the posterior extremity the double membrane which bounds the organism is broken by a pore 700 A in diameter.

Our sincere thanks are due to Mr P. Richmond for technical assistance, and we are grateful to the Central Veterinary Research Laboratory, Weybridge, for supplying the strain of Eimeria tenella.

This article investigates the impact of ego development on the course of psychiatric illness in a group of 37 psychiatrically hospitalized adolescents ages 12 to 16. The subjects, 21 males and 16 females, were evaluated at time of admission and again after 9 months of hospitalization. Using the Loevinger Sentence Completion Test (Loevinger, Wessler, & Redmore, 1970), two ego pathway groups were defined: progressors, those subjects who had advanced at least one-half stage in ego development, and nonprogressors, those who did not progress at least one-half state in ego development. Significant differences in clinical course were found between the two groups. Progressors demonstrated more significant decreases in psychiatric symptoms as measured by the Achenbach and Edelbrock (1987) Youth Self Report and had a significant change in their use of coping and defense processes compared with the nonprogressors. The findings are discussed in the context of a constructivist approach to developmental psychopathology.

Floe size within the Antarctic pack ice is an important parameter that affects both the ocean-ice-atmosphere energy exchange and the mechanical properties of pack ice. In this paper we present a computer-based algorithm to extract floe-size distribution information from digital aerial photographs of Antarctic sea ice. The algorithm segments digital images of sea ice into distinct floes from which the size of each floe is calculated and floe-size distributions are derived. Through a recursive application of the morphological erosion operator, each floe is eroded towards its centre while each pixel’s erosion number is recorded. This ensures no information is lost while individual floes are identified. The algorithm combines image-processing techniques with some manual input to accurately identify the boundaries of individual floes within an image. To demonstrate the functionality of the algorithm, six images, representing regions along a 22 km south-to-north transect through a transitional zone of pack ice near 65° S, 140° E, have been processed. Regional variations in the floe-size distributions show an increase in the number of smaller floes relative to larger floes and a decrease in the dominant floe size (in terms of areal coverage) from south to north. These results are consistent with ship-based observations.

Dr Corlett's paper on hydrodynamic interaction (Journal, 32, No. 2, May 1979) is of great interest, coming as it does from a practising naval architect with considerable experience of dealing with complex issues arising from casualty investigations. His paper gives an insight into the causes of interaction and the practical illustrations given in the paper add weight to his arguments.

Model experiments to study interaction between ships in shallow water have been undertaken at the National Maritime Institute for some years now and many of the results obtained agree with conclusions reached by Dr Corlett. For example experiments carried out with models close to sloping surface-piercing and flooded banks have shown that at moderate to high speeds the side forces and turning moments induced by the banks vary not as the square of the speed, but as the speed raised to a power greater than two. It is of interest to note that the rudder force used to counteract these bank effects varies roughly as the square of the speed, so that when close to a bank at too high a speed, use of the rudder is less likely to maintain control than would be the case at a more moderate speed.

The author correctly emphasizes the advantages of a ‘kick ahead’ with a single screw ship, but it is well to bear in mind that this device is not applicable to some ships, notably those with twin-screws and a single centreline rudder.