Introduction

Buffaloes contribute more than one-third of total milk production in Asia and are the second largest producer of milk in the world (Bandyopadhyay et al., 2003). Genital diseases occur with higher frequency in dairy animals, particularly in buffaloes (Ghora, 1995). In India, about 18-40 per cent of cattle and buffaloes were culled annually mainly due to infertility, low fertility or sterility (Sharma et al., 1993), which incriminates direct losses to the farmer as well as to the genetic resource. There are several types of cysts that can be found on the ovaries of the buffaloes, which can have a significant impact on the reproductive efficiency of the animal. The cystic structures that were studied included follicular cysts, luteal cysts, and cystic corpora lutea. The objective was to determine the potential causes of and factors affecting incidence of ovarian cysts in dairy cattle and to examine functionality of various preventative methods and treatments of cysts. This was performed through the review and presentation of pertinent information on the cystic ovarian conditions.

Each type of cyst is defined and its characteristics described in addition to its causes preventative methods and treatments. There is also information presented on the methods of differentiation between the cystic conditions as well as other anovulatory conditions that provide similar symptoms. Throughout the report, the different types of cysts are compared and contrasted in their characteristics, causes, and treatments so that connections are made between the different, yet remarkably similar, conditions (Lacey, 2010).

Materials and Methods

The samples were collected during the period March 2011 to October 2011 from the slaughterhouses located at Chennai. During the study period, ovaries of 1000 buffalo carcasses were examined. Both the ovaries were collected from 200 buffaloes where one or both the ovaries were apparently abnormal and subjected to detailed examinations for various conditions/affections. The tissue samples fixed in 10% NBF were processed by routine paraffin-embedding technique and 4-5 μm thick sections were prepared and stained by routine Haematoxylin and Eosin (H&E) for detailed histopathological studies (Luna, 1968).

In selected cases, adjacent sections of tissue samples were stained using special staining techniques which included Mc Manus method (PAS) for fungal elements.

Histochemical techniques were carried out for collagen (Masson’s trichrome and Van Gieson’s), mucin (Alcian blue and PAS) and calcium (von Kossa’s silver impregnation technique), as detailed by Luna, (1968).

Result and Discussion

Majority of the animals were aged. In the present study, the ovarian affections involving either the right or the left or the both were noticed in 200 (20%) cases. Ovarian affections were more in the right ovary than the left ovary. These affections occurred either singly or in combinations. The unilateral affections were more than the bilateral affections in the ovaries. Morphometry of the collected ovaries indicated that the length (right-2.96 ± 1.04, left-2.53 ± 0.99) and breadth (right 2.29 ± 0.69, left-1.99 ± 1.57) of the right ovary was significantly higher than the left ovary.

Based on the gross and histopathological findings, the cystic ovarian diseases were categorized as cyst within the ovary and cyst around the ovary.

Cyst within the Ovary

Follicular Cyst

Follicular cyst was recorded in 50 (25%) out of 200 buffaloes. Amongst all, unilocular cyst was seen in 10 cases and 40 revealed multilocular cysts with varying quantities of clear fluid. Grossly, the affected ovaries were large, round to oval shaped and had follicular cysts ranging from 1.2 to 3.1 cm comprising of clear cystic fluid, which became jelly like material on formalin fixation (Fig.1). These cysts were surrounded by thin wall. The cysts were usually seen in ovaries without corpus luteum. The weight of the ovary containing follicular cysts ranged from 7.20 to 13.30 g. Microscopically, the lumen of a single follicular cyst had thick eosinophilic fluid. The inner wall mostly lacked granulosa cell layer (Fig.2). In a few cases, the cysts were lined upto five layers of granulosa cells. These granulosa cells showed varying degree of degeneration and absence of germinal epithelium, cumulus oophorus and ovum (Fig.3). In most of the cases, the distinction between theca interna and theca externa was difficult and both the layers appeared as single layer. Ovarian stroma appeared compressed and atrophic in case of larger cysts.

The ovaries with multiple follicular cysts revealed 2 to 3 cysts of varying sizes containing clear or opalescent fluid. These cysts were seen on the surface as well as in the cut surface of the ovary (Fig.4). Microscopically there was moderate thickening of tunica albugenia along with mild lymphoid infiltration. Multiple cystic follicles were seen in the cortical area (Fig.5). The epithelium of these follicles appeared flattened and there was no cumulus oophorus and ovum inside them. Some of the cystic follicles showed the presence of moderate quantity of eosinophilic fluid. Medullary region showed medial thickening of blood vessels. In some of the cases vascular congestion was also noticed. The presence of anovulatory follicular cysts might also be due to the failure of luteinizing hormone to produce ovulation and subsequently affecting the proper development of corpus luteum (Robert, 1998). Ananda Raja and Srilatha (2007) reported 23 cases of follicular cyst in the ovaries.

Fig. 1: Ovary showing single large follicular cyst filled with watery fluid	Fig. 2: Follicular cyst showing absence of granulose cell layer. H & E x 200
Fig. 3: Follicular cyst with five layers of granulosa cells. H&E x100	Fig. 4: Cut surface of ovary showing multilocular follicular cysts
Fig. 5: Ovary-Multiple cystic follicles lined by varying layers of granulosa cells and mild lymphoid infiltration within the interstitium. H&E x 200

They further reported that the right ovaries more affected than left ovaries. The authors suggested that the prolonged continuous action of estrogen secreted from the cystic ovaries might have lead to chronic endometritis in these cases. The associated changes in reproductive tract can be due to hormonal imbalances resultant to the development of cysts (Dwivedi and Singh, 1975; Kumar 1981; Ghora, 1995). Luteal Cyst

Luteal cysts were noticed in 3 (1.5%) out of 200 buffaloes. Grossly, the ovaries were larger than normal, round in shape, yellowish in colour, which on palpation were soft and fluctuating. These ovaries with luteal cyst containing viscous fluid weighed from 5 to 8 g. The corpus luteum did not protrude from the surface of the ovary (Fig.6). The diameter of luminal cavity varied from 0.8-1.3cm. Microscopically, there was luteal tissue in place of granulosa cells, which was surrounded by a layer of connective tissue. Intermediate to large luteal cells of irregular shape with vacuolated cytoplasm and vesicular nucleus were seen amidst the connective tissue (Fig.7).

Fig. 6: Cut surface of ovary showing large, yellowish luteal cyst	Fig. 7: Luteal cyst showing single layer of granulosa cells surrounded by luteal tissue H&E x 400

According to Jubb et al. (1993), luteal cysts occur more frequently in cattle usually as unilocular cyst probably without adverse effect; however multiple cysts are mostly associated with infertility resultant to decreased level of secretion of luteinizing hormone to cause ovulation.

Cystic Corpus Luteum

Cystic corpus luteum was observed in 5 (2.5%) out of 200 buffaloes. The weight of the each ovary with cystic corpus luteum ranged from 1.5 to 6.5 g. grossly, the affected ovaries appeared normal, yellowish in colour with corpus luteum having an ovulation papilla on the top. The cut surface revealed hollow cavity containing clear or yellowish viscous fluid (Fig.8). The diameter of luminal cavity varied from 1.0-1.5cm. Microscopically, the wall of the cystic corpus luteum varied in thickness and had three layers. The central cavity contained eosinophilic fluid surrounded by loose connective tissue, which varied considerably in thickness depending on the size of the cavity. The middle layer had varying thickness of lutein tissue. The lutein cells were small polyhedral with eosinophilic cytoplasm and prominent nucleus. The outer layer was composed of tunica externa having interlacing and concentrically arranged bands of connective tissue (Fig.9). Robert (1998) stated that cystic corpus luteum was an ovulatory cyst. The cystic corpus luteum could be considered as non-pathological unless it did not produce adequate progesterone. Jubb et al. (1993) reported that cystic corpora lutea are not evidence of ovarian malfunction. They form after ovulation and do not affect the length of the estrus cycle and conception in cattle

Fig. 8: Cut surface of ovary showing single large, yellowish cystic corpus luteum	Fig. 9: Cystic corpus luteum lined by inner and outer fibrous layers with middle luteal tissue. H&E x400

Cystic rete ovarii

Cystic rete ovarii were noticed in 10 cases and revealed cystic dilatation, which appeared as irregular anastomosing cavernous spaces filled with serous fluid. The lining columnar cells revealed varying degree of hyperplasia at many places but focal atrophy as well as squamous metaplasia was also seen in a few areas. In addition, a few focal areas showed cystic structures with multilayered lining of squamous cells (Fig.10).

Fig. 10: Cystic rete ovarii showing irregular anastomosing cavernous spaces. H&E x400

Cystic rete ovarii has been commonly observed and the rete ovarii is mostly found associated with microfollicle. Higher incidences of rete ovarii viz. 75.69 and 29.69 per cent were reported by Dwivedi and Singh (1970) and Kumar (1981) respectively, whereas Rao and Rajya (1976) reported only in 0.59 per cent of cases.

Inclusion Cysts

Two cases (1%) of inclusion cysts were recorded in the present study. The cut surface revealed cystic structures near to the surface of ovaries. The weight of affected ovaries ranged from 4.2 to 5.3 g. Microscopically, cysts were lined by a single layer of cuboidal to flattened epithelial cells and contained clear watery fluid (Fig 11).

Fig. 11: Inclusion cysts lined by single layer of flattened epithelial cells. H&E x200

Inclusion cysts are called as fossa cyst in mares and develop close to the ovulation fossa. Most of these cysts are of no clinical significance, but large and multiple cysts can block ovulation (Jubb et al., 1993).

Cyst around the ovary

Parovarian cysts

This condition was noticed in 3 (1.5%) cases during the present study. Grossly the size of cysts varied from 0.4 to 1cm in diameter. The weight of affected ovaries ranged from 4 to 6 g. These structures were roughly spherical and located in the adjacent structure of ovary like bursa or fallopian tubes (Fig.12).

Fig. 12: Parovarian cyst containing clear watery fluid (arrow) located over the bursa

These cysts were covered by thin connective tissue capsule and contained clear watery fluid. Microscopically, the wall of the cyst was lined by single layer of cuboidal epithelium. Paraovarian cyst develops from the vestigial remnant of wolffian body and are not considered to have any adverse effect on reproductive potential of the animals (Dawson, 1963). However, if sufficiently enlarged in size, it can create problem in clinical diagnosis of ovarian lesions per rectum and thus is important from differential diagnosis point of view.

Disclosure of Interests

The authors have no conflicts of interest to declare. All authors participated and approved the article for publication.

Acknowledgement

Authors are the thankful to the Dean, Rajiv Gandhi Institute of Veterinary Education and Research, Pondicherry, India for providing the necessary facilities.

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