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Film: Development and transmission of Dirofilaria immitis
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LABORATORY MEETING
fluctuated. I n the initial stage of a primary infection before the worms are expelled from the intestine, the lung mast cells fall in numbers below those of the controls and lose their granules. Loss of granules from mast cells does not necessarily mean that the cells have died. F i l m : D e v e l o p m e n t and t r a n s m i s s i o n o f Dirofilaria immitis J. H. T H E I S * AND P. B. McGREEVY~- (INTRODUCED BY DR. R. L. MULLER)
*Department of Medical Microbiology, University of California, Davis, California tDepartment of Medical Helminthology, London School of Hygiene and Tropical Medicine This film was produced as a teaching aid for students of medical entomology and parasitology. T h e format of the film follows that of a scientific publication by including a brief introduction, materials and methods, results and discussion, and references. Though the entire life cycle of Dirofilaria immitis is demonstrated, emphasis is placed on the parasite's development in its experimental vector, Aedes aegypti. After presentation of colour diagrams of the mouthparts of the mosquito, the behaviour of the vector during blood engorgement is examined in detail. Microfilariae are demonstrated in blood smears from an infected dog followed by their migration through the engorged midgut to the distal ends of the Malpighian tubules. First, second, and third stage filarial larvae are shown with a brief discussion of their morphological characteristics. Special emphasis is placed on the transmission of infective form larvae including their emergence from the tip of the labellae and their migration onto the surface of the skin of the vertebrate. T h e film concludes by showing adult filariae in the right ventricle of an infected dog and comments on the distribution of the parasite in the United States. ENTOMOLOGY Hymenopteran egg-parasite of triatomine bugs D. S. B E R T R A M
Department of Entomology, London School of Hygiene and Tropical Medicine T h e hymenopteran egg-parasite of South American species of triatomine bug, Telenomus fariai, was discovered as parasitic in eggs of Panstrongylus megistus by COSTA LIMA (1927). I t has since been studied by numerous workers in South America using eggs of different bug species as host-eggs, in particular more recently by RAmNOVICH et al. (1970) in Venezuela in a series of papers. T h e potential of egg-parasites for biological control of triatomine vectors of Chagas's disease adds particular interest to such studies. T h e exhibit displayed a mounted ~ and ~ of the Scelionid hymenopteran, Gryon triatomae, an egg-parasite of the bug Triatoma rubrofasciata from India, and also several bug eggs showing debris within the egg and the large aperture in the chorion through which the Gryon adult emerged on completion of its development in the egg. A pinned adult T. rubrofasciata was also shown. T h e material was obtained by courtesy of Dr. F. J. Simmonds and Dr. V. P. Rao of the Commonwealth Institute of Biological Control, India, from their colonies of T. rubrofasciata and G. triatomae in India. T h e acceptability of eggs of some South American triatomine species to Gryon triatomae for its normal development is being investigated in London. REFERENCES COSTA LEMA, A. DE (1927). Sciencia Med., 5, 450. RAmNOVlCH, J. E. et al. (1970). J . med. Era., 7, 477. 1. 2. 3.
T h e effect o f h e p a r i n on the m i g r a t i o n o f Brugia pahangi m i c r o f i l a r i a e in Culex pipiens T h e u p t a k e o f B. pahangi m i c r o f i l a r i a e in C. pipiens a n d the i n f e c t i v i t y o f C. pipiens in r e l a t i o n to m i e r o f i l a r i a l d e n s i t i e s E v i d e n c e o f a s e x - l i n k e d r e c e s s i v e gene, sb, c o n t r o l l i n g s u s c e p t i b i l i t y o f C. pipiens t o B. pahangi B. A. O B I A M I W E AND W. W. M A C D O N A L D
Sub-Department of Entomology, Liverpool School of Tropical Medicine 1. In a strain of Culex pipiens refractory to Brugia pahangi only 1% of the microfilariae migrated successfully to the thorax when the mosquitoes were fed on a donor cat; in a
LABORATORY MEETING
fluctuated. I n the initial stage of a primary infection before the worms are expelled from the intestine, the lung mast cells fall in numbers below those of the controls and lose their granules. Loss of granules from mast cells does not necessarily mean that the cells have died. F i l m : D e v e l o p m e n t and t r a n s m i s s i o n o f Dirofilaria immitis J. H. T H E I S * AND P. B. McGREEVY~- (INTRODUCED BY DR. R. L. MULLER)
*Department of Medical Microbiology, University of California, Davis, California tDepartment of Medical Helminthology, London School of Hygiene and Tropical Medicine This film was produced as a teaching aid for students of medical entomology and parasitology. T h e format of the film follows that of a scientific publication by including a brief introduction, materials and methods, results and discussion, and references. Though the entire life cycle of Dirofilaria immitis is demonstrated, emphasis is placed on the parasite's development in its experimental vector, Aedes aegypti. After presentation of colour diagrams of the mouthparts of the mosquito, the behaviour of the vector during blood engorgement is examined in detail. Microfilariae are demonstrated in blood smears from an infected dog followed by their migration through the engorged midgut to the distal ends of the Malpighian tubules. First, second, and third stage filarial larvae are shown with a brief discussion of their morphological characteristics. Special emphasis is placed on the transmission of infective form larvae including their emergence from the tip of the labellae and their migration onto the surface of the skin of the vertebrate. T h e film concludes by showing adult filariae in the right ventricle of an infected dog and comments on the distribution of the parasite in the United States. ENTOMOLOGY Hymenopteran egg-parasite of triatomine bugs D. S. B E R T R A M
Department of Entomology, London School of Hygiene and Tropical Medicine T h e hymenopteran egg-parasite of South American species of triatomine bug, Telenomus fariai, was discovered as parasitic in eggs of Panstrongylus megistus by COSTA LIMA (1927). I t has since been studied by numerous workers in South America using eggs of different bug species as host-eggs, in particular more recently by RAmNOVICH et al. (1970) in Venezuela in a series of papers. T h e potential of egg-parasites for biological control of triatomine vectors of Chagas's disease adds particular interest to such studies. T h e exhibit displayed a mounted ~ and ~ of the Scelionid hymenopteran, Gryon triatomae, an egg-parasite of the bug Triatoma rubrofasciata from India, and also several bug eggs showing debris within the egg and the large aperture in the chorion through which the Gryon adult emerged on completion of its development in the egg. A pinned adult T. rubrofasciata was also shown. T h e material was obtained by courtesy of Dr. F. J. Simmonds and Dr. V. P. Rao of the Commonwealth Institute of Biological Control, India, from their colonies of T. rubrofasciata and G. triatomae in India. T h e acceptability of eggs of some South American triatomine species to Gryon triatomae for its normal development is being investigated in London. REFERENCES COSTA LEMA, A. DE (1927). Sciencia Med., 5, 450. RAmNOVlCH, J. E. et al. (1970). J . med. Era., 7, 477. 1. 2. 3.
T h e effect o f h e p a r i n on the m i g r a t i o n o f Brugia pahangi m i c r o f i l a r i a e in Culex pipiens T h e u p t a k e o f B. pahangi m i c r o f i l a r i a e in C. pipiens a n d the i n f e c t i v i t y o f C. pipiens in r e l a t i o n to m i e r o f i l a r i a l d e n s i t i e s E v i d e n c e o f a s e x - l i n k e d r e c e s s i v e gene, sb, c o n t r o l l i n g s u s c e p t i b i l i t y o f C. pipiens t o B. pahangi B. A. O B I A M I W E AND W. W. M A C D O N A L D
Sub-Department of Entomology, Liverpool School of Tropical Medicine 1. In a strain of Culex pipiens refractory to Brugia pahangi only 1% of the microfilariae migrated successfully to the thorax when the mosquitoes were fed on a donor cat; in a