Serodiagnosis of Foot and Mouth Disease (FMD) Virus for Differentiation Between Naturally Infected and Vaccinated Cattle and Buffaloes
Suzan A. Hassanein,
Wafaa Abd El-Wahab,
Mervat M. Mahmoud
FMD is a highly contagious viral disease of all cloven-footed animals and widely distributed all over the world. In this study, 465 serum samples were collected from 3 Nile delta governorates (Behaira, Mounofya and Kafer El-Sheikh) during 2009. The samples were used for detection of FMD antibodies to 3ABC non-structural proteins using commercial ELISA kit (Priocheck). The over all percentage of positive was 38.9%. The higher percentage of positive detected in Behaira (48%), then Mounofya (45.3%) while Kafer El-sheikh was the lowest (23.7%). The positive results of detection of antibodies against non structured proteins of FMDV indicate that these samples come from natural infected animals.
to cite this article:
Suzan A. Hassanein, Wafaa Abd El-Wahab, Moustafa Eweis and Mervat M. Mahmoud, 2011. Serodiagnosis of Foot and Mouth Disease (FMD) Virus for Differentiation Between Naturally Infected and Vaccinated Cattle and Buffaloes. International Journal of Virology, 7: 198-203.
June 20, 2011; Accepted: August 27, 2011;
Published: October 22, 2011
FMD is one of the most contagious epidemic diseases of livestock can spread
very rapidly. It is caused by 7 immunologically distinct serotypes, O, A, C,
Asia 1, South African Territories (SAT) 1, SAT 2 and SAT 3 which belong to the
species Foot-and-mouth disease virus (genus Aphthovirus, family Picornaviridae).
Several of these serotypes circulate currently or periodically in the Middle
East and North Africa (Knowles and Samuel, 2003). It
is characterized by the formation of vesicles in and around the mouth and on
the feet, it reduces feeding and often causes lameness. Abortion, sterility,
permanent decline in milk yield, decrease in meat production and reduction in
breeding ability are common sequelae. Mortality can result and although low
for adult animals, can be higher than 50% in the young. The virus needs to be
eliminated to re-establish disease-free status; failure would have serious economic
consequences (Commission of the European Communities, 1989;
Early warning is therefore essential to detect an incursion while it is still
localized. Early and decisive reaction is required if the disease is to be contained
and eventually eliminated without serious socio-economic consequences. To be
effective, the control measures must be applied in the shortest possible time
is crucial to success. Cattle are regarded as good indicator hosts, whereas,
sheep tend to show few clinical signs and are often considered maintenance hosts
for a relatively short period where movement and transport can be responsible
for virus spread. Infected animals may excrete the virus for up to a few days
before exhibiting clinical signs. A proportion of recovered cattle, African
buffaloes and sheep remain virus carriers for variable periods. Wild or feral
ruminant or porcine animal populations may act as reservoirs for infection.
Direct contact between animals is the most significant method of transmission,
but the virus may persist for considerable periods in the environment (particularly
in temperate climates) and mechanical transmission by fomites is also considerable.
Windborne spread over considerable distances is possible in temperate climates.
Inactivated vaccines are widely used for FMD but vaccine strains must be carefully matched to prevailing field virus strains if a satisfactory level of protection is to be attained; vaccination cover must attain a level of at least 80% for effectiveness. Serological tests that allow discrimination between antibodies resulting from infection and vaccination (NSP ELISA tests) are now becoming available and should permit more accurate monitoring of control and eradication programmes based on mass vaccination. FMD vaccination is, unfortunately, still carried out in a haphazard manner in many countries, resulting in the disease remaining endemic for long periods.
A test which differentiates the vaccinated and infected animals antibodies
would be of great value in FMD control. Several tests which are based on Non-Structural
Proteins (NSP) have been described (Berger et al.,
1990; Neitzert et al., 1991; Bergmann
et al., 1993; Lubroth and Brown, 1995). For
the screening of large numbers of samples an ELISA would be highly preferable.
An indirect-trapping ELISA for the detection of antibodies against 3ABC has
been reported (De Diego et al., 1997). The sensitivity
of the essay on experimental sera post-infection was reported to be 100%. The
specificity was reported to be more than 99%.
In Egypt, routine prophylactic vaccination has been conducted with a locally
produced serotype O vaccine. The last outbreak of serotype O was in June 2000
and other serotypes have not been reported since 1972 when serotype A occurred
(Ferris and Dawson, 1988). OIE (2006)
and Knowles et al. (2007) described an FMD serotype-A
virus responsible for recent outbreaks of disease in Egypt.
This study describes the using of commercial PrioCHECK, FMD NS ELISA kit, to cattle and buffaloes populations and the application of the developed kits to the serological surveillance system to monitor the progress of the FMD control program in three Nile Delta Governorates.
MATERIALS AND METHODS
Samples: Sera were randomly collected from vaccinated cattle and buffaloes in three Egyptian Governorates (Behaira, Mounofya and Kafer EL-Sheikh). Age of animals ranged from less than one year to more than 2 years. The samples data is showing in Table 1.
||Number of serum samples of cattle and buffaloes in relation
to the age
|*Age class-1 (age less than 1 year), **Age class-2 (age less
than 2 year), ***Age class-3 (age more than 2 year)
||Results of PrioCHECK, NSP of FMDV ELISA test
||Seropositive percentage by Priocheck FMD NSP in relation to
|*Age class-1: Age less than 1 year, **Age class-2: Age less
than 2 year, ***Age class-3: Age more than year
ELISA kit: The commercial PrioCHECK, FMD NS ELISA kit for in vitro
detection of antibodies against FMD virus in serum of cattle, sheep, goat and
pigs. The kit is used according to its instructors. Samples give percent of
inhibition IP≤50% considered negative and that give IP≥50% considered
Statistical analysis: This analysis was conducted using excel and Pivot table.
As shown in Table 2 the number of over all positive samples are 181 samples out of 465 samples (38.9%). The highest present of positive were found in Behaira Governorate (48%), Mounofya Governorate (45.3%) and the lowest one was Kafer El sheikh Governorate (23.7%). The positive percent in buffaloes (36.9%) was lower than cattle (40.21%) in the over all samples. Although, the percent of positive in buffaloes (54%) is higher than that of cattle (45%) in Behaira Governorate and buffaloes (25.9%) is higher than that of cattle (22.44%) in Kafer El sheikh Governorate.
As shown in Table 3 the percent of positive according to age at less than one year, less than 2 year, more than 2 years are respectively, 36.5, 39.29 and 40.2%, respectively. The highest percent of positive found at samples collected from animals more than 2 years. While the lowest found at samples collected from animals less than one year.
Foot and Mouth Disease (FMD) is the major disease constraint on international
trade in livestock and their products. Effective vaccines and control measures
have enabled the FMD unvaccinated, seronegative herds in compliance with strict
international trade policies. However, the disease remains enzootic in many
regions of the world; it is a serious problem for commercial trade with FMD-free
countries (Bhattacharya et al., 2005).
Vaccination plays an important role in the control of FMD in Asia, Middle East,
Africa and South America. In most FMD-free countries a non-vaccination policy
is in place. Recent outbreaks in Europe clearly demonstrated the risk of this
policy. Using conventional diagnostic techniques, up to now it was not possible
to distinguish FMD infected animals from purely vaccinated animals. In vaccinated
areas disease control authorities had limited possibilities to monitor virus
presence or circulation (Van Aarle, 2001). Art-vaccines
are based upon highly purified antigens which are free from Non-Structural Proteins
(NSP) of the FMD virus. Other vaccines may be partly purified and contain a
reduced amount of NSP. Animals, antibodies against the Structural Proteins (SP)
but not against NSP. Modern, state of the FMD virus infection induces antibodies
against both SP as well as NSP. NSP-free or NSP-reduced vaccines in combination
with a NSP-test lead to a so called marker-system (Van Aarle,
2001). An ELISA using baculovirus-expressed 3AB and 3ABC as the antigens
has been demonstrated to successfully differentiate vaccinated from infected
cattle and sheep (Sorensen et al., 1998).
In May 2006, the new bivalent vaccine was locally produced containing both O1 and A/Egypt/2006 local isolates and used for routine vaccination of Egyptian animals.
The results of PrioCHECK ELISA test in this study proved the presence of antibodies
against NSP of FMDV in cattle and buffalo population in Behaira, Mounofya and
Kafer EL-Sheikh Governorates which may be attributed to natural infection of
FMDV. The percent of positive was 38.9%. A proportion of vaccinated animals
can become sub- clinically infected if they are subsequently exposed to the
homologous virus and may be able to transmit infection for up to 14 days after
vaccination, even when they become immune to the development of clinical disease
(FAO), or due to the impurity of the inactivated vaccine (Chung
et al., 2002).
As shown in Table 2, the number of total positive samples
is 181 samples out of 465 samples (38.9%). The highest present of positive are
found in Behaira Governorate (48%), Mounofya Governorate (45.3%) the lowest
one is Kafer El sheikh Governorate (23.7%). Recent outbreaks were reported in
Behaira Governorates in September 2007 and January 2008 by serotype O (FAO,
The positive percent in buffaloes is lower than cattle in the over all samples
(36.9%). This may be indicate the presence of high resistance of buffaloes to
FMDV than cattle this is agreed with Ghoneim et al.
(2010). Although, the percent of positive in buffaloes (25.9%) is higher
than that of cattle (22.44%) in Kafer El sheikh Governorate.
As shown in Table 3, the percent of positive according to
age at less than one year, less than 2 year, more than 2 years are respectively,
36.5, 39.29 and 40.2%. The highest percent of positive found at samples collected
from animals above 3 years. While the lowest found at samples collected from
animals less than one year. This indicates that the immunity afforded by vaccines
does not last long (Geering and Lubroth, 2002).
To apply the differentiating diagnostic tool, the sera from vaccinated cattle
and buffaloes would be preferred for evaluating the usefulness of these kits.
The immune response to nonstructural proteins has been reported to develop later
than that to structural proteins in the course of infection (De
Diego et al., 1997; Sorensen et al., 1998).
Following experimental infection, antibodies to the 3ABC antigen could not be
detected earlier than 8 and 10, days in cattle, sheep (Sorensen
et al., 1998), respectively. Since, all positive sera described in
this report were collected from cattle and buffaloes vaccinated with FMD vaccine,
the actual time of the first FMDV contact was unknown. Therefore, the earliest
time after infection that the assay could detect an immune response to the 3AB
antigen was undetermined.
As described above, the 3ABC PrioCHECK, FMD NS ELISA has promising sensitivity and specificity to distinguish FMDV-infected animals from vaccinated animals. This kit has also been demonstrated to be useful for monitoring the progress of the FMD eradication program in Egypt.
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