Haematological observations in rabbits infected with T. brucei

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N o v e l a p p a r a t u s for the m i c r o s c o p i c o b s e r v a t i o n o f p r o t o z o a n c u l t u r e s P. L. C H I O D I N I

Protozoology Department, IVellcome Research Laboratories, Beckenham, Kent A vessel was designed in which intra-erythrocytic protozoa could be cultivated and high power light microscopic observation made of culture in situ via a central observation well. The central observation well was made from a 50 ml. glass syringe, the barrel and plunger of which were cut at right angles to their longitudinal axes. The cut ends were then ground flat. A glass coverslip was attached to one end of the plunger using Araldite. T h e edges of the coverglass were ground flush to the surface of the plunger so that it could move freely in the cut barrel. The barrel was mounted in a glass jacket fitted with 3 access ports. T h e base of the glass jacket was ground flat and an optically flat sheet of glass joined to it with Araldite. T h e barrel and base plate were so arranged that the longitudinal axis of the barrel was perpendicular to the optically flat glass, so that when the plunger was depressed the coverglass and base plate met face to face. Culture material is introduced to the vessel through a serum cap via a hypodermic needle. The inner sleeve is depressed and a layer of culture of uniform thickness, normally a cell monolayer, is trapped between coverglass and base plate, permitting observation under an oil immersion objective introduced down the centre well of the culture vessel. T h e layer of culture is still in contact with the rest of the culture ,and therefore remains under the same conditions during the period of observation; a considerable advantage over conventional wet preparations. The inner sleeve may be raised between observations, so that separate random samples are obtained at each observation. Introduction of, for example, a gas supply, inhibitors, fresh cells or parasites can be undertaken via the serum caps.

Acknowledgement I am most grateful to Mr. R. Newman for his expert assembly of the apparatus.

S c h i s t o s o m e s as t h e v e h i c l e s o f s a l m o n e l l a i n f e c t i o n S T U A R T W. Y O U N G , G E N E H A G A S H I AND R E F A A T K A M E L United States N A M R U-3, Cairo, Egypt Living S. mamoni were removed from 2 patients with chronic salmonellosis using the extra-corporeal filtration technique and colonies of S. paratyphi A were cultured from their surface. Immunofluorescence microscopy revealed many colonies of S. paratyphi A on and within the surface tissues of the schistosomes. This is thought to be the first clear demonstration of a bacteria-parasite interaction within a human host; the tegumental colonization of schistosomes by Salmonella may predispose the schistosome infected patient to the chronic S. paratyphi A infection.

H a e m a t o l o g i c a l o b s e r v a t i o n s i n r a b b i t s i n f e c t e d w i t h 7". brucei G. C. J E N K I N S , C H R I S T I N E M. FORSBERG, JEAN BROWN, F. E. B O U L T O N AND C. W. PARR

Department of Haematology, The London Hospital Medical College A series of observations were made in which the haematological data of sandy-lop rabbits infected with T. brucei $42 (obtained from Dr. D. Godfrey at the Lister Institute) together with normal controls were demonstrated. The results presented showed the decrease in red cell counts, platelet counts, haemoglobin and packed cell volttmes with the concomitant increase in the proportion of reticulocytes and red cell pyruvate kinase levels. During the course of the infection thin blood films showed the presence of low parasitaemia and several types of abnormal red ceils. Bone marrow samples taken when the animals were moribund showed hyperpLasia of the erythroid series and a proportionately greater number of trypanosomes than seen in the thin blood films.

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F r o m our preliminary experiments, including some data not presented here, it would appear that at least one type of anaemia associated with experimental T. brucei infections in rabbits is a normochromic haemolytic anaemia. T h e mechanism of the red cell destruction is being investigated further. T h e effects o f a p r e v i o u s i n f e c t i o n w i t h f i l a r i a s i s i n t h e c o t t o n rat o n a s u b s e q u e n t infection

W. E. K E R S H A W , P. D. W E L L S , D. M. S T O R E Y #, A. B I N G H A M , M. S. E N Y A T , P. R. R A T N A P A L A AND F. A. K. A L - B A L D A W I

Department of Biology, University of Salford *Now at Department of Chemistry and Biology, Sheffield Polytechnic F o r the last 10 years, we have been investigating the relation between the nutrition and genetics of the host and filariasis in the rat. W e have shown that effects are produced by protein calorie deficiency, vitamin E deficiency and vitamin A deficiency on two of the components of this host/vector/parasite combination and that these effects are different in different genetic strains of rat. These investigations have been made possible by devising methods of measuring the exposure to infection in the laboratory and comparing them with the worms established later. So far, we have concerned ourselves with first infections in animals not previously exposed to infection. We are now investigating whether similar effects are produced by nutritional deficiencies in multiple infections. T h e experiments reported here establish precise measured relations between first and second infections and show that a first infection retards the development of the worms of a second infection. I t does not reduce the number of worms developing. A second infection may cause an abrupt and unexpected fall in the number of microfflariae in the circulation produced by the first infection. Some 15 years ago, our former colleague, Professor Bertram, showed that superinfection with filariasis in the cotton rat produced partial suppression of subsequent infections. Our detailed results with this precise method conform with his ideas. Dugbe virus: a new tick-borne arbovirus from Nigeria

T A M . S. D A V I D - W E S T (introduced by Dr. J. S. Porterfield)

Virology Division, National Institute for Medical Research, Mill Hill, London Dugbe virus is a new arbovirus isolated at the Virus Research Laboratory, Faculty of Medicine, University of Ibadan, Nigeria. T h e virus was named after the district of the city of Ibadan, where the prototype strain was isolated. T h e first isolate was from ticks (Amblyoma variegatum). However, isolations have also been made from domestic livestock, from culicoides, and from mosquitos; of particular interest are 4 isolates made from humans. U p to 1969, 744 isolates of the virus were made; of these 549 isolates were made from ticks, making about 54% of the total isolates. T h e virus was routinely studied in baby mice, which were inoculated intracerebrally. In this animal paralysis and encephalitis were manifestations of the infection. Highly sensitive tissue culture system (PS cells) has been developed at Mill Hill. This system could go a long way in facilitating further studies of the virus. T h e virus is now routinely titrated by the micro-plaque method (MADmD and PORTERFIELD: W H O Bull., 40, 113-121, 1969). Discrete, clear and round plaques are produced, and are stainable from day 4 after infection. I n the plaque assay a strong prozone phenomenon is produced in the lower dilutions (10 -1 and 10-z). I t has been shown that the phenomenon is highly specific for the virus strain, i.e. "protected" cells resisted superinfection with Dugbe virus or serologically related viruses, while viruses unrelated to Dugbe virus replicated normally. SimuUidae of Pakistan

D. J. L E W I S

External Staff, Medical Research Council; care of British Museum (Natural History) Specimens and drawings of some of the 31 species now known from Pakistan were shown. Simulium indicum, which belongs to a new subgenus, Himalayum, has been reported