healthmedicinet

The prevalence of Echinococcus parasites revealed a relatively high level of infection that requires an effective
anti-parasite control programme. According to the studies conducted in different countries,
the estimated prevalence of dog Echinococcus parasites vary from 5 to 70 % 15], 52], and some factors such as geographical location, sampling protocols, demographic
factors, anthelmintic usage, and diagnostic techniques are responsible for the wide
range of Echinococcus prevalence.

The potential role of stray dogs as definitive reservoir hosts for Echinococcosis
has been recognized as a significant public health problem worldwide; however few
morpho-molecular studies have been carried out based on the identification of different
aspects of adult E. granulosus s. l. originating from stray dogs 29], 30], 53]–55].

In Table 1, the lowest infection (2 of 16) was found in older dogs (7 years old) than other
age groups (3 and 3-7) because they develop acquired immunity to re-infection in
endemic areas although, no meaningful correlation was found between parasitism and
age groups based on statistical analysis 56].

The infection rate of E. granulosus s. l. among stray dogs was 20 % which there is no concordance with previous study (prevalence
12.5 %) 57]. It is associated with a lack of controlling infected dogs, increasing of unsanitary
slaughter around the city and non-normative expulsion of infected viscera of intermediate
hosts which are potential ways in transmission of disease 13], 15], 58].

It is worth mentioning that the genotyping of adult Echinococcus strains can indicate the scale of parasite biology in the region, while this shows
that the intermediate hosts may acquire the infection from neighboring countries/provinces
due to their immigrations and importations whereas, the stray dogs are sympatrically
limited to an indigenous life 12], 13].

In this study, existence of genotypes G1 and G3 of E. granulosus show that sheep and buffalo are unambiguously circulating in the region.

In this study the camel strain was first found in a stray dog. As regards to previous
reports, this seems to indicate that the role of secondary intermediate hosts (buffalo/goat/sheep/cattle)
which can potentially play a role in the maintenance of camel-dog life cycle 10], 12], 59]. On the one hand, translocation of infected dogs from exceptional regions is the
main suspected cause of the introduction of the G6 infection in the region.

In this study, presence of mixed infection of E. granulosus has already been explained in the liver and lungs of single animals 60], 61]. This is described by a single infection due to a definitive host concurrently harboring
adult worms of the two genotypes or due to consecutive infections of the intermediate
host.

To date, the rostellar hooks morphology to be hard, not changeable, quick and inexpensive
method is believed as a valid criterion for discriminating Echinococcus strains 17], 29], 37], 62]–65].

Nevertheless, some researchers believe that employing morphometric criteria alone
for the recognition of E. granulosus strains are not responsive enough and other complementary characteristics must be
considered 66], 67].

The rostellar hook measurements from G1 strain were not considerably different from
those G6 and G3 strains whilst, Harandi et al.68] show that the G6 genotype is readily distinguishable from G1 by using both small
and large hook lengths in intermediate hosts (hydatid cyst samples of livestock and
human origin). They also demonstrated that the total large hook length can help to
distinguish the G3 and G6 genotypes. These contradictory results are revealed by two
facts. First, the morphometric keys cannot always be considered as a well-known criterion
in discrimination of Echinococcus strains in both intermediate and/or definitive hosts due to various growth patterns
of parasites in developmental stages (metacestode or adult). Second, due to the low
number of G3 and G6 strains in this study, it should be investigated on one more sample
size.

Generally, the size and shape of hooks are variable through the parasite’s development
which supports our findings based in Table 3. These differences may explain why dogs are usually infected with collected protoscolices
from several hydatid cysts, whilst the sample of protoscoleces for hook measurements
frequently comes from a single cyst. However, if contamination of intermediate hosts
is achieved through heterogeneous sources 30] it is probable that the hook measurements of adult worms are genetically different
from the protoscoleces, and subsequently lead to differences in hook measurements.

High haplotype diversity (Hd 0.873) identified in stray dog population are alerted
to pathogenecity range of E. granulosus/E. canadensis complexes, the creation of emergent strains in under studied areas and also the resistance
of adult worms versus host innate immunity responses, including apoptosis 6], 69], 70].

The intraspecies variations among some G1 sequences provide evidence of which mechanisms
of slippage, unequal crossing over/transposition and genetic drift/founder effect
have led to the variation in Echinococcus species 71]. Also, it seems that the lack of any bottleneck effects in the under studied areas
and the long term geographic segregation into the regions are probable heterogeneity
assumptions 72].