Discussion
The highly pathogenic avian influenza (HPAI) virus generally causes
severe outbreaks in poultry population. However, occasionally HPAI
infect humans exposed to infected poultry. The HPAI-H5N1 outbreak
confirmed in this study have been implicated in previous outbreaks in
many African countries including Nigeria, Egypt, Côte d’Ivoire, Burkina
Faso, Niger and Cameroun [10,17]. In Cameroun, two strains of HPAI;
H5N1 and H5N8 were isolated in outbreaks that occurred on commercial
farms in 2016 affecting birds with mortality rates ranging between 8%
and 96%. In Ghana, previous outbreaks of HPAI (H5N1 and H9N2) have been
reported in many regions since the first outbreak in 2007 [10,11].
The circulating H5N1 and H9N2 strains in Ghana have been reported to be
homologous to that observed in Nigeria, Burkina Faso and other West
African countries, suggesting a potential cross-border contamination of
bird species [10,11]. The low mortality rate; 9% and 13%, observed
on Case farms 2 and 1 respectively in the current study, are similar to
those previously reported in the West Africa region [18]. This may
be explained by the similarity in the strains identified in the region.
Our study revealed concerning findings of how birds were moved between
farms without inspection by regulatory bodies at the entry points of the
district. Even more concerning was how one of the affected farmers moved
dead and sick birds back to the farm (source) in the neighboring region
for replacement without detection. These lapses contributed to the
importation and subsequent spread of the HPAI outbreak in the affected
farms. Similar links with poor regulation, were shown in previous HPAI
outbreaks [9,10,17,19]. The key sources of the transmissions of HPAI
previously reported includes unregulated movements of poultry and eggs
dealers from one farm, market, or town to another without appropriate
preventive care as well as poor biosecurity measures on farms and live
poultry markets [17]. In Nigeria, similar biosecurity
non-compliances have been implicated in H5N1 and H5N8 outbreaks
occurring between 2014 and 2017 [7]. Similar lapses in biosecurity
measures were implicated in HPAI outbreaks globally especially in Europe
and Asia [20–23]. The poor regulation of movement of animals have a
potential to affect trade negatively in the future.
Owing to the difficulties in restricting the movement of poultry in many
settings, some control strategies implemented in previous HPAI outbreaks
in Egypt include mass vaccination, surveillance and preemptive culling
of infected birds [9]. In Ghana, control measures utilized in
previous HPAI outbreaks involved depopulation of all birds on affected
farms, disinfection of affected farms, and restricted movement of
poultry and poultry products after which, active influenza surveillance
is initiated among birds, domestic poultry, and the human population
[10]. These measures were equally effective in the current outbreak
response. The depopulation of all birds on affected farms, disinfection
of farms and live bird market, and ban on sale and movement of live
birds during the current outbreak response, contributed to a successful
control of the outbreak. Similar control measures have been used in
other settings with success [9,21]. The collaborative efforts of
both human and animal health personnel through a One Health approach as
well as the legislation and enforcement by the municipal assembly
through the municipal coordinating council also contributed largely to
containment and prevention of further spread of the infection in the
present outbreak.
Although human cases of HPAI have been reported in 15 different
countries following outbreaks in birds including in Hong Kong [21],
Thailand [24], Turkey [25], Egypt [26] and Cameroon
[17], none of the human contacts in our study developed flu-like
symptoms after two maximum incubation periods follow-up. Almost all of
the human cases reported in previous avian influenza outbreaks were
caused by zoonotic transmission from poultry and disproportionately
affects women and their children. This is because women and children
were observed to be more exposed when nursing birds raised in backyard
farms compared to adult males who are less involved on the backyard
farms [9]. Transmission generally depends on every country’s own
dynamics associated with raising poultry and other intrinsic immunologic
susceptibility to the infection. Nevertheless, transmission of HPAI from
poultry to humans continues to be rare, despite frequent and widespread
close contact between humans and affected poultry [27]. However, our
study could not assess how and why the human contacts were asymptomatic
after follow-up.
The effects of avian influenza outbreaks are often devastating for
farmers. Generally, the economic consequences of these outbreaks are
severe, since it results in culling of all affected birds and their eggs
[28]. To alleviate the impact of losses suffered on farmers and
encourage farmers to report bird deaths, payment of financial
compensation to farmers is common in some settings including in Egypt
[9] and the United States of America [29]. Although compensation
was not paid to the affected farmers in the present outbreak, the
farmers were educated and counselled to prevent future outbreaks.
Public Health Actions
The affected farmers were informed of laboratory confirmation of HPAI-H5
on Saturday June, 23 2018. The farmers were educated on the essential
biosecurity measures to adopt to mitigate future occurrences. They were
sensitized on the need for regular hand washing with soap and running
water after attending to the poultry. The health facilities within the
municipality were also placed on high alert for influenza-like illnesses
and any unusual events.
The Municipal Assembly initiated a ban on the sale and movement of birds
from affected farms. Similarly, a ban on the sale of live birds at the
Nkawkaw market was also instituted. A depopulation exercise was
conducted on June 26, 2018. A pit of about 3 meters high was dug with an
excavator and the birds transported in a container to the pit together
with all the eggs found on the farms. Carbon dioxide foam concentrate
was sprayed on the birds in the pit before they were covered with a soil
layer of about 2 meters. Disinfection of the live bird market was
conducted on June 27, while the infected farms were disinfected on June
30, 2018. The farms were cleared of remaining litters and beddings and
the decontamination of the pens done using Izal solution.