International Journal of Aquaculture, 2018, Vol.8, No.5, 29-37
34
The recruitment process of the parasitic fauna of
E. sardella
in the study was dominated by cestodes. According to
Rusuwa et al. (2014), the cestodes were identified as
Ligula intestinalis
. The present study indicated that
Ligula
intestinalis
(cestodes) and
Camallanus sp.
(nematodes) identified in the fresh
E. sardella
were common during the
dry season and the rainy season. The cold season registered no prevalence of the parasites. Barson and Marshall
(2003) observed the prevalence of
L. intestinalis
in
Barbus paludinosus
with no clear seasonal variations but
suggested that the dry season had an effect on the prevalence. This is in agreement with the results of the present
study which show no prevalence of parasites during the cold season and higher prevalence during the dry season.
In contrast to the findings of the study, Anarse et al. (2011) reported no prevalence of cestodes during the rainy
season but prevalence in the cold season and summer with the highest prevalence rate. Wetzel (2001) attributes
the prevalence of
L. Intestinalis
to an increase in number of copepods which are numerous in stagnant than in
running water bodies while Anarse et al. (2011) attributes the prevalence to temperatures that facilitate the
hatching of the eggs. Copepods are intermediate hosts of
L. intestinalis
(Piasecki et al., 2004) while the larvae of
Camallanus sp.
are secreted into the water with the fish faeces and ingested by copepods or other crustaceans
which are eaten by the other fish hosts where the larvae develops into a full adult (Yanong, 2006). On the other
hand, Dejen et al. (2006) reported that during the rainy season the infection reduced due to increased turbidity that
decreased the feeding efficiency on the zooplankton. They observed that the infection rate in
Barbus humilis
was
high in the clear water than in the shallow turbid water. This implies that habitat changes have some significant
effect on the infection rate of the fish. This could be the case because the piscivorous birds could predate more
efficiently on the fish in shallow and clear waters than in the turbid and deep waters. Sharma (2016) reported the
prevalence of three cestodes parasites in the intestines of freshwater fish,
Channa punctatus
with the highest
infection in summer season, followed by winter and lowest in monsoon. Rusuwa et al. (2014) reported the
infection of
L. intestinalis
throughout the year. This is contrary with the findings of this study where there is no
infection observed during the cold season.
E. sardella
is an endemic species in Lake Malawi and breeds (spawns)
throughout the year (Morioka and Kaunda, 2004). Therefore the difference between the findings of this study and
that of Rusuwa et al. (2014) on the prevalence of
L. intestinalis
during the cold season could emanate from other
factors like; feeding, habitat type, presence of the intermediate hosts and other environmental factors, such as
temperatures, turbidity and depth of the water body. The study showed that fish were infected with large numbers
of parasites in the latter part of the cold season to end of the dry season. Since most helminths parasites utilize the
food chain for their transmission (Dejen et al. 2006), the differences in the prevalence rate of the parasites could
be due to difference in habitat, food supply for both the intermediate host and aquatic piscivorous birds that play
an important role in the completion of the life cycle of the parasites (Ibrahim and Soliman, 2010). According to
Piasecki et al. (2004), the main food of
E. sardella
in the lake are zooplankton, which act as intermediate hosts of
L. intestinalis
. Procercoid larvae in copepod develop into plerocercoid in the fish abdominal cavity (Loot et al.,
2006). Therefore the fluctuations in the abundance of the zooplankton could also affect the prevalence rate of the
L. intestinalis
during the different seasons of the year among other factors. The fact that the study reveals the
presence of
Ligula intestinalis
should be a cause of concern in public health because it may result in the
prevalence of ligulosis in humans. There are reports of human infestation with
Ligula intestinalis
(Barson and
Marshall, 2003; Urdes and Hangan, 2013). This entails that if
E. sardella
is not handled properly, humans could
be affected by the parasite. However, Ljubojevic et al. (2015) emphasized that the most important risk factor for
the spread of the fish-borne parasitic zoonoses is the consumption of raw and undercooked fish meat. This
suggests that proper preparation of
E. sardella
which host the parasite could help avert the dangers posed by the
parasite.
4 Conclusion and Recommendations
The study rejected the null hypothesis on the seasonal parasitic load in
E. sardella
. The results indicated seasonal
variations in the prevalence rates of the parasites in the fresh
E. sardella
. The dry season had the highest
prevalence rate followed by the rainy season and lastly the cold season. The study indicated a strong interaction of
the parasites with the environment, the host fish and other factors that have some bearing on the cycles of the
parasites. Finally, the study indicated that water parameters, variations in fish behaviour, seasonal variations and
effective parasite stages were some of the contributing factors to the proliferation of the parasites. This study
