Book Volume 1
Natural and Anthropogenic Drivers of Viral Emergence
Page: 1-17 (17)
Author: Johanna F. Lindahl* and Bernard Bett
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Abstract
Emerging infectious diseases are causing outbreaks with loss of human and
animal lives and may have large economic and societal impacts. There may be both
natural and anthropogenic drivers behind the emergence of viral diseases. Zoonotic
diseases are more commonly emerging, and because RNA viruses have an inherent
tendency to change, they are overrepresented among emerging diseases. Apart from the
naturally occurring changes in the pathogens, humans also contribute to disease
emergence by contributing to changes in land use and climate, which in turn affects
ecosystems and biodiversity. This chapter reviews the different mechanisms behind
viral disease emergence, as well as presents a framework evaluating the spill-over of
zoonotic diseases at the human-wildlife-livestock interfaces. The chapter starts with
discussing viral evolution and moves towards global changes and the impact on
diseases, with a particular focus on vector-borne viruses.
Infectious Laryngotracheitis Virus: Molecular Biology, Pathobiology, and Control Strategies
Page: 18-40 (23)
Author: Muhammad A. Shahid*, Ahmad J. Sabir, Muhammad I. Arshad, Sadeeq ur Rahman, Muhammad F. Tahir, Muhammad N. Zahid and Muhammad A. Zahoor
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Abstract
Infectious laryngotracheitis (ILT) is an economically important respiratory
disease of chickens that is prevalent throughout the world. It is caused by an infectious
laryngotracheitis virus (ILTV), also named Gallid alphaherpesvirus 1 (GaHV-1). It is a
member of the genus Iltovirus, subfamily Alphaherpesvirinae, family Herpesviridae
and order Herpesvirales. The ILTV genome is a linear double-stranded DNA molecule
with an average genome length of 151,607 nt. Twelve herpes simplex virus -1
homologue genes have been identified in the ILTV genome, with seven of them,
glycoproteins B, C, H, K, L, M and N, present in the UL region, while glycoproteins D,
E, G, I and J are present in the US region of the ILTV genome. Although chicken is the
natural host of ILTV, infections have also been reported in pheasants, pheasant-chicken
crosses, peafowls, turkeys, and ducks. An incubation period of 3–12 days is followed
by an acute phase of the infection which lasts 1–2 weeks. During this phase, the virus
replication occurs in the conjunctiva, trachea, and larynx, resulting in conjunctivitis,
gasping, coughing, and expectoration of blood-mixed mucus. ILTV infection results in
decreased weight gain and egg production. It causes 0 to 80% mortality depending on
the virulence of the strain involved. Like other herpesviruses, ILTV establishes latent
infection in trigeminal ganglia and virus reactivation and shedding occur following
various stress factors.
ILTV infections are generally diagnosed by the typical clinical signs and detection of
intranuclear inclusion bodies in the affected tissues. Furthermore, the detection of
virus-specific antigen by fluorescent antibody, immunohistochemical staining of
smears and tissues, detection of DNA by a polymerase chain reaction, and virus
isolation by inoculating embryonated chicken eggs or cell cultures can also be
performed. Virus neutralization assays and different types of ELISAs have also been
established. To control ILTV infections, a combined effort is required encompassing
prompt disease diagnosis, the use of geographic information system technology,
biosecurity, vaccination, differentiation of infected from vaccinated (DIVA), and
eradication of reservoir hosts.Abstract
Solving the complications of oncogenesis caused by retroviruses is a
challenging task for veterinary and biomedical scientists. Avian Leukosis viruses
(ALVs) are a group of avian oncogenic retroviruses that can cause neoplastic diseases
in chickens. The viral invasion starts due to the interaction between glycoproteins in
the viral envelop and receptor sites of host cells. The pathogenesis of ALVs could be
explained by three theories which include promoter insertion, enhancer activation, and
the presence of oncogenes in their genome. Additionally, these viruses show great
diversity due to the high mutational rate that enables them to escape from the action of
the host immune system and antiviral drugs. Therefore, due to the high mortality rate of
chickens, ALVs are responsible for huge economic losses in the poultry industry. Due
to horizontal & vertical transmission and genetic variations, there is no effective
vaccine to prevent infections of ALVs.
The aim of this chapter is to summarize various research aspects related to the
pathogenesis and transmission of ALVs. It is essential to understand these processes to
get further insight into the biology of ALV’s. Likewise, to design the control strategies
for ALV infections, it is invaluable to explore the interactions between ALVs and host
immunity.
Abstract
Rabies lyssavirus (RABV) is the main lyssavirus involved in rabies, a 100%
lethal zoonotic acute encephalitis. Cats, like other mammals, are susceptible to the
disease, and this is an emerging concern regarding feline health and Public Health as
rabid cats might transmit the disease to humans. Transmission to cats occurs from other
cats or canids, but bats are of growing concern as reservoirs to feline rabies. Upon
infection, RABV spreads via axons to the central nervous system (CNS) and leads to
either the paralytic or the furious form of the disease, depending on the immune
response and the virus strain. A definitive diagnosis is based on immunofluorescence
and virus isolation in cell cultures or mice using post-mortem samples of CNS; PCR is
of value in cases of poorly conserved samples and DNA sequencing is of uttermost
importance for the molecular epidemiology of rabies. Vaccination using an inactivated
virus is the core preventive measure regarding cats.
Canine Distemper: Current and Emerging Perspectives
Page: 61-69 (9)
Author: Abdullah Iqbal*, Farhan Mushtaq and Shumaila Manzoor
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Abstract
Canine distemper virus can cause infections in domestic canines and in
many wild animals belonging to families Canidae, Felidae, Hyaenidae, Procyonidae,
Ailuridae, Ursidae, Mustelidae, Viverridae and some non-human primates. Among six
proteins encoded by the genome of the virus, genetic drift has been associated with the
hemagglutinin protein. Based on phylogenetic analysis of different strains, the virus is
categorized into six groups. RT-PCR, ELISA, indirect fluorescent antibody test, serum
neutralization test and immunohistochemistry can be used for diagnosing canine
distemper. Recombinant canarypox vectored vaccine is currently used for the
prevention of the disease in domesticated canines, but now researchers are focusing on
the development of new vaccines with new strains of the virus from different genetic
groups.
Emerging Trends in Epidemiology, Diagnosis and Control of Bovine Leukemia Virus
Page: 70-80 (11)
Author: Zanib Khan*, Muhammad Abubakar, Nazish Bostan and Muhammad Javed Arshed
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Abstract
The bovine leukemia virus (BLV) is responsible for the enzootic bovine
leukosis, an infectious lympho-proliferative disease of the cattle. This can result in
economic fatalities for the cattle industry as it is responsible for the low productivity
and low milk production, higher early culling in turn increasing the death rates with
high charges on the prevention measures of the outbreaks. This chapter summarizes the
occurrence, diagnosis, preventative, and therapeutic approaches in managing bovine
leukemia.
West Nile Virus
Page: 81-89 (9)
Author: Abdullah Iqbal*, Shumaila Manzoor and Muhammad Abubakar
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Abstract
West Nile virus (WNV) is an arthropod-borne RNA virus, first time isolated
in 1937 from Uganda. Now, WNV has been reported from throughout the world virus
with 9 possible phylogenetic lineages. Mosquitoes of the genus Culex are mainly
responsible for WNV transmission to birds and humans. In horses, WNV cause the
disease, and the infected horse suffers from lethargy and nervous disorder. WNV
causes West Nile virus disease in humans, which is characterized by skin rash, fever,
vomiting and sometimes neurological disorder. In contrast to the WNV vaccine in
animals, no vaccine against WNV is commercially available for humans. For veterinary
use, RecombiTEK is a commercially available recombinant vaccine against WNV.
WNV can be detected in horses by serological tests like hemagglutination inhibition,
ELISA, and plaque reduction neutralization or by necropsy of the brain. People who
have direct contact with birds and horses are more prone to WNV exposure than others.
Hendra: An Emerging Viral Disease in Equine
Page: 90-96 (7)
Author: Sami Ullah Khan Bahadur*, Razia Kausar and Usman Talib
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Abstract
Number of diseases have been emerged in the recent past and many of these
have been emerged with a new fate. Hendra is a newly emerged disease of horses and
humans. Members of the family Paramyxoviridae infect numerous species but with
host specificity. Hendra virus of this family has become more important due to its
zoonotic potential. Fruit bats have been considered as an asymptomatic reservoir host
for this virus due to high seroprevalence against Hendra virus, earlier called “horse
morbillivirus.” Horses become affected after ingesting contaminated material polluted
with fruit bat urine. Disease transmission from horses to humans occurs while touching
the horse’s fluids. Hendra is a fatal disease and causes death within a few days
following the appearance of the clinical picture. Clinical signs involving the respiratory
and nervous systems are evident during the disease course. Postmortem lesions are also
associated with the lungs. Electron microscopy, Immunofluorescence, PCR and ELISA
are laboratory diagnostic tools for Hendra. With the advancement of the world, the load
of emerging diseases is increasing. Although Hendra has not been considered as a
widespread disease yet but is a transboundary threat, so there is a need to control it. A
Viral G glycoprotein-based vaccine has been produced in Australia against the Hendra
virus. For the control of this disease, handling of infected horses and vaccination are
important strategies.
Abstract
Rabies is known to humans since long time. Rabies is a viral disease that
induces neuro-encephalitis and produces 59,000 casualties globally on an annual basis.
Once the viral pathogen produces neurological symptoms, the disease is almost 100%
fatal. Despite of this risky condition, the disease is preventable through timely
administration of post-exposure preventive measures (PEP) and/or pre-exposure
prophylactic measures (PrEP). About 15 million heads receive PEP annually
throughout the world. This chapter provides updated information on advances in rabies
research from its epidemiology, transmission, immunopathology, clinical disease,
patient management, and prophylaxis measures. This chapter will also discuss the
technical framework for rabies control through advanced strategies of vaccination,
surveillance, laboratory diagnosis, animal movement monitoring, and research.
Internationally, the WHO and OIE are committed to formulating a comprehensive
methodology for the control of rabies of human and animal origin by the year 2030.
Conclusively, this chapter will widely focus on those aspects for rabies elimination
globally.
Abstract
SARC-CoV belongs to the group beta-coronavirus of the family
Coronaviridae, the largest RNA viruses. First emerged from China in 2003, it spread to
other parts of the world in the following year. A closely related MERS-CoV was
reported in 2013 with 30-90% fatality. The virus contains four structural proteins (S, E,
M, and N) along with non-structural and accessory proteins involved in viral
pathogenesis and virulence. The virus mainly spreads through aerosols; bats are
reservoir hosts; human-human transmission is also reported. It attacks lungs’ tissue by
virus-specific ACE2 receptors. Pro-inflammatory cytokines and chemokines increase
during infection. Fever, pain, and dyspnea are important clinical signs, and death
occurs due to acute and severe respiratory distress. Autopsy lesions resemble the HPAI
H5N1 strain. RT-PCR is mainly used for accurate detection of the virus. No specific
treatment or vaccine is available at this stage, but certain drugs like ribavirin have
shown potential results.
Potential Reservoirs of Viral Zoonotic Disease
Page: 120-129 (10)
Author: Abdullah Iqbal* and Muhammad Abubakar
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Abstract
One-third of infectious diseases have a zoonotic origin. Rapid urbanization
and industrialization have affected the environment and increased the chance of
spillover of different viral zoonotic pathogens. Viral epidemics of zoonotic origin are
now becoming a menace for humanity. The most notable example is the COVID-19
pandemic that spread all over the world within weeks. Different animals such as bats,
canines, non-human primates and birds act as reservoir hosts of many viruses. Sudden
amplification of these viruses by amplifier hosts can lead to drastic outcomes.
Researchers from different biological fields should work in liaison for a better
understanding of genetic factors of viruses that can become the source of sudden
mutation and increased pathogenicity and transmission to other hosts.
Introduction
Advances in biochemistry, molecular biology, virology, and structural biology have enabled the researchers in veterinary medicine to make many exciting discoveries that have, in some cases, conceptually revolutionized our understanding of the discipline. Emerging Trends in Veterinary Virology is a review of selected topics about viral infections in animals. 11 chapters cover recent findings about specific viruses that infect a variety of hosts. The contents cover several types of veterinary infections in birds (Infectious laryngotracheitis (ILT), avian leucosis), cats (feline rabies), dogs (canine distemper), bovines (viral leukemia) and equines (hendra virus disease). Additionally, special topics such as the epidemiology of veterinary zoonoses and SARS are also covered. The book provides updated information for researchers (virologists, microbiologists), students and veterinarians, alike.