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Gaipova Mutabar Ergashevna, Tashkent State Agrarian University, Tashkent, Uzbekistan E-mail: ushakarbaev@mail.ru Akramova Firuza Djalaliddinovna, Institute of Zoology, Academy of Sciences of the Republic of Uzbekistan Tashkent, Uzbekistan E-mail: f.akramova1976@mail.ru Shakarbaev Ulugbek Abdulakimovich, Institute of Zoology, Academy of Sciences of the Republic of Uzbekistan Tashkent, Uzbekistan E-mail: ushakarbaev@mail.ru Azimov Djalaliddin Azimovovich, Institute of Zoology, Academy of Sciences of the Republic of Uzbekistan Tashkent, Uzbekistan E-mail: ushakarbaev@mail.ru Saparov Kalandar Abdullaevich, Tashkent State Pedagogical University Tashkent, Uzbekistan E-mail: ka_biologiya@mail.ru
NEW DATA ON THE BIOLOGY AND LOCALISATION OF NEMATODE SETARIA LABIATOPAPILLOSA (ALESSANDRINI, 1838)
Abstract: The paper provides the results of research into some aspects of the biology of nematode S. labiato-papillosa, as well as its localisation, distribution and life cycles in Uzbekistan. Blood sucking Diptera, such as Aedes caspius, Culex pipiens, Culex hortensis and Stomoxys calcitrans, were identified as the nematode's intermediate hosts. Cx. hortensis was identified as the intermediate host of S. labiatopapillosa for the first time. The numbers of blood sucking Diptera are the highest in summer and early autumn. The rate of infection with larvae of S. labiatopapillosa in the biocoenoses of Uzbekistan is 0.3-1.3%. Populations of mature S. labiatopapillosa were for the first time recorded in the lymphatic system of cattle. This is the first recorded case of the presence of this Setaria species in animals' lymphatic system.
Keywords: Setaria, biology, distribution, localisation, lymph nodes, Uzbekistan.
1. Introduction S. labiatopapillosa in Uzbekistan [2; 12]. These and other studies
Nematodes Setaria labiatopapillosa (Alessandrini, 1838) helped us broaden and deepen considerably our knowledge in are found on all continents except Antarctica. Populations of this species and discover a number of interesting aspects in the mature Setaria tend to parasitise cattle and many other ani- biology and distribution of the nematode in question. mal species. The nematode has long since become a focus of The currently available data on Setaria is highly insuffi-
researchers' attention, as S. labiatopapillosa causes chronic cient. The best studied category is mature nematodes, which, diseases in various animals. The circulation of the infection is however, also pose a number of questions. Very often this spe-fascilitated by various blood sucking Diptera, which take part cies is recorded in a wide range of animal species, which act as in the nematode's life cycle as intermediate hosts [4; 8; 10; 11]. definitive hosts, but this issue has not been analysed properly
The growing interest in this nematode species in recent years yet [3, 14]. Nor is there a clear idea of where in the organism has resulted in deeper research into the biology and life cycle of of a definitive host this nematode is localised.
This paper reports on the results of research into the biology and distribution of S. labiatopapillosa of cattle across the biogeocoenoses of Uzbekistan. Also the article discusses some issues about the localisation of mature nematodes in their definitive hosts.
2. Material and metods
This work is based on the material that resulted from long-term (2010-2018) and comprehensive faunistic and experimental research into S. labiatopapillosa in the biogeocenoses of Uzbekistan. During these years we studied many individuals of cattle at slaughterhouses and meat-packing plants in the Republic of Karakalpakstan and 12 provinces of Uzbekistan. Common helminthological methods [13] were used to collect Setaria from the abdominal cavities and lymph nodes. A total of 975 individuals of cattle were examined. Traditional parasitological identification methods were used to identify species of mature Setaria [14].
At the same time, we collected blood sucking Diptera from the familes Muscidae, Culicidae and Simulidae and examined them for larvae of Setaria. Dozens of thousands of Diptera individuals were examined in areas the animals concentrate in spring, summer and autumn. Common laboratory and experimental methods were used in the research [1; 6; 8; 10].
3. Results and discussion
One species of Setaria, S. labiatopapillosa, was recorded in cattle throughout Uzbekistan. The average infection rate in the studied animals was 35.8%. The prevalence ranged between 20.0 and 50.0%. The intensity was between 1 and 45 individuals.
In the biogeocoenoses of Uzbekistan S. labiatopapillosa was recorded in cattle in various altitudinal zones - flatlands, foothills and mountains. The infection rate is strongly dependent on the type of landscape. The highest rate was recorded on flatlands covering most of the north-western (Khorezm province and the Republic of Karakalpakstan) and northeastern (Tashkent, Syrdarya and Jizakh provinces) parts of Uzbekistan, 50% and 45% respectively. The prevalence and intensity of infection in cattle drop considerably with altitude (20-25%). Mature nematodes were localised in different parts of the abdominal cavity in all 350 infected individuals. In 123 of the 350 infected individuals of cattle, that is, 30.5%, mature S. labiatopapillosa were recorded in the lymph nodes of the mesentery. This is the first case this Setaria species was recorded in the lymphatic system.
Most researchers consider that mature forms of S. labiatopapillosa parasitise most often in different parts of the abdominal cavity [3; 12; 14]. The reliability of records about this nematode species present in other organs, such as the intestine, eyes, brain and kidneys, is very doubtful [14]. The doubts are based, on the one hand, on the unclear identification of the
existing species from the genus Setaria, on the other hand, on the methodological errors.
Nevertheless, the analysis of literary sources and the results of our research, in particular, those concerning the localisation of S. labiatopapillosa in the lymphatic system of cattle [2], helped us establish a number of tendencies and mechanisms allowing a different view on Setaria's life cycle and biology.
A comparative analysis of the occurrence of this Setaria species in various organs in cattle shows that the commonest localisation is the abdominal cavity. The nematodes can also concentrate in the lymph nodes of these animals.
Setaria males and females formed tangles in the lymph nodes ofthe mesentery. The intensity ofthe infection ranged between 3 and 7 individuals. Up to 19 individuals of the nematode were recorded in some lymph nodes. The lymph nodes affected by granulomatous lymphadenitis were much larger in size. The concentration of large numbers of nematode individuals in a node also affected the integrity of this node. In some cases the pathologically deformed nodes broke, letting the nematodes out into surrounding cavities. It is possible that microfilariae brought by females concentrate in cavities in lymph nodes and their vessels, and later get into blood vessels and accumulate in peripheral vessels. This quite accounts for the work of mechanisms dispersing micofilariae of S. labiatopapillosa across the organism of their definitive vertebrate hosts.
Morphologically, the populations of mature S. labiatopapillosa collected in the abdominal cavity and lymph nodes were almost identical (fig. 1, Table 1). The slight variations in the body length of male and female nematodes from the abdominal cavity and lymph nodes are negligible from the diagnostic aspect.
In its definitive host (cattle) S. labiatopapillosa is localised in both the abdominal cavity [5; 14] and the lymphatic system [2].
The fact that we discovered S. labiatopapillosa in cattle's lymphatic system is, probably, an indication of a successful completion of its life cycle by this nematode. The thing is that recently borne microfilariae are enwrapped in a case made of the thin and transparent eggshell 0.24-0.32 mm long and having a maximum width of 0.006-0.007 mm. In this condition microfilariae cannot penetrate into blood vessels directly from the abdominal cavity. They can free themselves from the case only when they have got into the stomach of a carrier (mosquito), after which they begin migrating most actively through the walls of the insect's stomach into its chest muscles [4; 7]. Based on these statements, we believe that microfilariae borne by female S. labiatopapillosa and localised in the lymphatic system of the definitive host play an important role. This conclusion is, obviously, relevant to the life cycles of other Setaria species localised in the same parts of the body.
Figure 1. Setaria labiatopapillosa (Alessandrini, 1838): a - mature nematodes from the lymph nodes of the mesentery; b - lymph node of a domestic bovine animal infected with Setaria
Vertebrate animals become infected with S. labiatopapillosa transmissively, when mosquitoes - Aedes caspius, Culexpipiens, Culex hortensis and stable flies - Stomoxys calcitrans, the parasite's intermediate hosts in Uzbekistan, suck their blood. This usually takes place in warm seasons, from June to late October. Animals may be infected on pastures (Stomoxys calcitrans), in cattle farms and in pens (Ae. caspius, Cx.pipiens, Cx. hortensis).
Table 1.- Size of Setaria labiatopapillosa from the abdominal cavity and lymph nodes of cattle (n = 10), mm
The intermediate hosts - mosquitoes and flies - are quite common in natural biocoenoses and cattle farms. Their numbers are large in summer and early autumn. The rate of infection with S. labiatopapillosa in blood sucking Diptera in the biocoenoses of Uzbekistan is 0.3-1.3% (Table 2).
Признаки Abdominal cavity Lymph nodes
lim M ± m C v lim M ± m C v
Males:
Body length 46-51 48.53 ± 0.55 0.04 46-48 47.35 ± 0.27 0.02
Body width 0.44-0.50 0.473 ± 0.01 0.04 0.44-0.50 0.473 ± 0.007 0.04
Oesophagus length 7.8-10.4 9.06 ± 0.32 0.11 7.8-10.2 8.829 ± 0.29 0.10
Tail length 0.17-0.20 0.186 ± 0.003 0.06 0.17-0.20 0.186 ± 0.003 0.06
Spicule lenght: - left 0.36-0.38 0.371 ± 0.002 0.02 0.36-0.40 0.375 ± 0.005 0.04
- right 0.12-0.14 0.129 ± 0.002 0.07 0.12-0.14 0.129 ± 0.003 0.06
Lateral appendages
on the rear end of the 0.06-0.07 0.0653 ± 0.001 0.05 0.06-0.07 0.0653 ± 0.001 0.05
body
Females:
Body length 60-92 76.3 ± 4.1 0.17 58-91 76 ± 4.1 0.17
Body width 0.44-0.70 0.558 ± 0.03 0.15 0.44-0.66 0.546 ± 0.02 0.12
Oesophagus length 7.8-9.8 8.7 ± 0.26 0.09 7.8-9.8 8.7 ± 0.26 0.09
Tail length 0.38-0.58 0.483 ± 0.02 0.15 0.38-0.58 0.483 ± 0.022 0.15
Vulva at the front end 0.46-0.76 0.619 ± 0.04 0.18 0.46-0.76 0.619 ± 0.04 0.19
Lateral appendages
on the rear end of the 0.09-0.12 0.1058 ± 0.003 0.10 0.09-0.12 0.106 ± 0.003 0.10
body
Table 2.- Rate of infection with larvae of Setaria labiatopapillosa in blood sucking Diptera in the biogeocoenoses of Uzbekistan
Species Inds. studied, No. Infected
No. of inds. %
Muscidae
Liperosia irritans 5639 - -
Liperosia titillans 4010 - -
Stomoxys calcitrans 989 8 0.9
Simulidae
Simulium flavidum 5850 - -
Odagmia ornata 7940 - -
Freisia alajensis 5824 - -
Culicidae
Culex pipiens 5950 81 1.3
Culex modestus 4365 - -
Culex pusillus 4145 - -
Culex hortensis 2178 6 0.2
Aedes caspius 2030 7 0.3
Anopheles hyrcanus 2125 - -
In flat areas between 0.3% and 1.3% of blood sucking insects are infected with larvae of S. labiatopapillosa, while in foothills (Cx. hortensis) their portion is 0.2% or less. Microfilariae are known to be sucked out of cattle together with blood by their intermediate host, get into the latter's stomach, free themselves from the case and migrate into the insect's chest muscles, where they grow into the infective stage. Further they migrate within a mosquito (or fly) from the muscles to the proboscis. The 3rd- stage invasive larvae have a body between 2.2 mm and 2.56 mm long and 0.040-0.044 mm wide (fig. 2). The invasive larvae penetrate into the blood of their definitive host through the skin damaged by the biting of blood sucking Diptera. They further migrate to the lymphatic system and abdominal cavity, where they evolve to maturity.
The most recent data obtained in the XXIst century have made great changes in our idea about the biology and localisation of the nematode under study based on the material collected during the long period since the beginning of the investigation into this nematode in the XIIIVth century until the late XXth century.
The group of this nematode's intermediate hosts in the biogeocoenoses of Uzbekistan comprises four Diptera species: Stomoxys calcitrans (Muscidae), Culex pipiens, Culex hortensis and Aedes caspius (Culicidae). The results of our research expand the well-known data [4; 5; 7; 8; 10; 11] on the intermediate hosts of S. labiatopapillosa. Thus, around 15 species of insects from the families Muscidae and Culicidae have been identified as the intermediate hosts of S. labiatopapillosa,
whose 3rd-stage larvae develop in the organisms of the above-mentioned insects. The evolution from the microfilaria to the infective stage in mosquitoes (Culex pipiens, Culex hortensis and Aedes caspius) and flies (Stomoxys calcitrans) takes 10-12 days at a temperature of 28-30 °C. The infective larvae were up to 2.20-2.52 mm long, and males could be differentiated from females.
Figure 2. Setaria labiatopapillosa (Alessandrini, 1838): infective larva from the proboscis of Culex hortensis (original)
The study of the intermediate hosts of S. labiatopapillosa carried out herein confirmed the data [9] about flies - Stomoxy scalcitrans - participating in the life cycle of this nematode. We can confirm that within the range of S. labiatopapillosa both mosquitoes and stable flies may act as the parasite's intermediate hosts and facilitate the spread of Setaria under study.
4. Conclusion
According to the current research, cattle in the biogeocoenoses of Uzbekistan are infected with only one Setaria species - S. labiatopapillosa. Populations of mature Setaria were detected in 350 of 975 examined bovine animals, which is 35.8%. The intensity of the infection ranged between 1 and 45 individuals. The infection rate was between 20.0 and 50.0%, depending on the region.
Animals become infected with S. labiatopapillosa trans-missively, when mosquitoes - Aedes and Culex - and flies -Stomoxys calcitrans are sucking their blood. The infection is
highest in warm seasons, between June and October. This is supported by the sporadic infection of intermediate hosts with the parasite's larvae.
In the definitive host S. labiatopapillosa are localised in the abdominal cavity and the lymph nodes of the mesentery. Newly born microfilariae easily get to the blood system and
concentrate in peripheral vessels. This quite accounts for the work of mechanisms dispersing micofilariae across the organism of their definitive host.
The work was carried out within the framework of a fundamental project by the Academy of Sciences of the Republic of Uzbekistan - VA-FA-F-5-007.
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