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Category: Clinical Microbiology
Flying Foxes, Horses, and Humans: a Zoonosis Caused by a New Member of the Paramyxoviridae, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816940/9781555811211_Chap04-1.gif /docserver/preview/fulltext/10.1128/9781555816940/9781555811211_Chap04-2.gifAbstract:
This chapter describes the outbreaks of disease caused by Megamyxovirus zoonotic agent; provides an updated description of the virus, its genome, and its wildlife reservoir; and documents what is known of the pathology and pathogenesis of equine morbillivirus (EMV) infection. A severe outbreak of respiratory disease occurred in the second half of September 1994 in horses stabled in the Brisbane suburb of Hendra. The outcome of the outbreak was that 13 horses died. The trainer died after hospitalization with severe respiratory involvement, while the stable hand recovered after a protracted illness. Although horses had been moved off the property during this period, infection had not spread to distant sites and extensive surveillance showed that the virus was not active in horses or humans. In fluorescent-antibody tests, sera from naturally infected horses and humans reacted strongly with the fruit bat virus. Identical viruses were isolated from a range of tissues from horses infected during the initial outbreak and from a kidney of the deceased trainer. Morphologically the virus is a member of the family Paramyxoviridae. The pathology of field and experimental EMV infections in horses and experimental infections in cats has been described. It is sufficiently different from known members of the Paramyxoviridae to be considered a member of a new genus which bridges the two existing genera Paramyxovirus and Morbillivirus. The author proposes that consideration should be given to creating a new genus within the family Paramyxoviridae, subfamily Paramyxovirinae, to be called Megamyxovirus, with the type species being EMV.
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Map of Australia showing the locations of both EMV outbreaks and the combined distribution (shaded area) of the four flying fox species. P. alecto, P. conspicillatus, P. poliocephalus, and P. scapulatus. NSW, New South Wales; NT, Northern Territory; QLD, Queensland; SA, South Australia; TAS, Tasmania; VIC, Victoria; WA, Western Australia.
Map of Australia showing the locations of both EMV outbreaks and the combined distribution (shaded area) of the four flying fox species. P. alecto, P. conspicillatus, P. poliocephalus, and P. scapulatus. NSW, New South Wales; NT, Northern Territory; QLD, Queensland; SA, South Australia; TAS, Tasmania; VIC, Victoria; WA, Western Australia.
A male grey-headed flying fox (P. poliocephalus).
A male grey-headed flying fox (P. poliocephalus).
Polyacrylamide gel electrophoresis of purified EMV. The left lane contains molecular mass markers, and the right lane contains EMV proteins.
Polyacrylamide gel electrophoresis of purified EMV. The left lane contains molecular mass markers, and the right lane contains EMV proteins.
Genome structure of EMV. The top diagram represents the sequenced part of the EMV genome, with the shaded boxes indicating protein-coding regions. The numbers in parentheses after the protein name represent protein sizes in amino acid residues, while the sizes of noncoding intergenic regions are indicated in nucleotides with downward-pointing open arrows. The vertical bars between genes represent the position of intercistronic sequences, which are highly conserved in EMV. The solid arrows at each end of the genome indicate that there are still sequences at the termini which need to be cloned and characterized. The table at the bottom summarizes the comparison of sizes (in nucleotides) of coding and noncoding (the latter indicated by two letters separated by a slash) regions of EMV, hPIV3 and MV. The numbers in parentheses are sizes of protein products in amino ac ids. The question marks indicate information yet to be acquired.
Genome structure of EMV. The top diagram represents the sequenced part of the EMV genome, with the shaded boxes indicating protein-coding regions. The numbers in parentheses after the protein name represent protein sizes in amino acid residues, while the sizes of noncoding intergenic regions are indicated in nucleotides with downward-pointing open arrows. The vertical bars between genes represent the position of intercistronic sequences, which are highly conserved in EMV. The solid arrows at each end of the genome indicate that there are still sequences at the termini which need to be cloned and characterized. The table at the bottom summarizes the comparison of sizes (in nucleotides) of coding and noncoding (the latter indicated by two letters separated by a slash) regions of EMV, hPIV3 and MV. The numbers in parentheses are sizes of protein products in amino ac ids. The question marks indicate information yet to be acquired.
(Top) Tissue section from a lung of the first horse inoculated in the laboratory with EMV•infected spleen. blood, and lung cells. The horse developed severe pulmonary edema in 8 days. The figure shows pulmonary edema and hemorrhage as well as a venule with a prominent syncytial cell, regarded as characteristic of this infection. Hematoxylin-eosin stain; original magnification, ×400. (Bottom) Tissue section from a kidney of a horse infected with EMV in the field. There are positive reactions to an indirect immunofluoresccnce test for EMV, particularly in a glomerulus. Original magnification, ×430.
(Top) Tissue section from a lung of the first horse inoculated in the laboratory with EMV•infected spleen. blood, and lung cells. The horse developed severe pulmonary edema in 8 days. The figure shows pulmonary edema and hemorrhage as well as a venule with a prominent syncytial cell, regarded as characteristic of this infection. Hematoxylin-eosin stain; original magnification, ×400. (Bottom) Tissue section from a kidney of a horse infected with EMV in the field. There are positive reactions to an indirect immunofluoresccnce test for EMV, particularly in a glomerulus. Original magnification, ×430.
(Top) A lung of a horse examined at necropsy 5 days after parenteral inoculation with EMV. Surface lymphatics are clearly distended with gelatinous fluid. (Bottom) The opened thorax of a cat at necropsy 7 days after subcutaneous inoculation with EMV. This cat and others characteristically developed severe hydrothorax as well as congestion, hemorrhage, and edema in the lungs.
(Top) A lung of a horse examined at necropsy 5 days after parenteral inoculation with EMV. Surface lymphatics are clearly distended with gelatinous fluid. (Bottom) The opened thorax of a cat at necropsy 7 days after subcutaneous inoculation with EMV. This cat and others characteristically developed severe hydrothorax as well as congestion, hemorrhage, and edema in the lungs.
(Top) Tissue section from the brain of a guinea pig 9 days after subcutaneous inoculation of EMV. A perivascular cuff of lymphocytes can be seen. Hematoxylin-eosin stain; original magnification, ×280. (Bottom) Tissue section from the brain of the same guinea pig as in the top panel. This section had been stained for an indirect immunoperoxidase test for EMV. Reactions occurred within neurons, confirming tropism for this tissue. Original magnification, ×320.
(Top) Tissue section from the brain of a guinea pig 9 days after subcutaneous inoculation of EMV. A perivascular cuff of lymphocytes can be seen. Hematoxylin-eosin stain; original magnification, ×280. (Bottom) Tissue section from the brain of the same guinea pig as in the top panel. This section had been stained for an indirect immunoperoxidase test for EMV. Reactions occurred within neurons, confirming tropism for this tissue. Original magnification, ×320.
Summary of serum EMV-neutralizing antibody results for fruit bats collected in Queensland in 1996
Summary of serum EMV-neutralizing antibody results for fruit bats collected in Queensland in 1996